A Tetrahedral Counterpart to Ramanujan-Nagell Trinagular Numbers?

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[Edit] Apologies for the typo in the title. "Trinagular" should read "Triangular." [/Edit]
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No x > 8, for x an element of N, satisfies the following equivalency: 3/2 * Tetra_(x-1) = 2^y -2 for any y an element of N

====================================================================
for Tetra_x is the x-th Tetrahedral Number --> (n*(n+1)*(n+2))/3!

This Conjecture has been computer checked to 100,000,000 and I have been told that not only is a proof possible, but it is so "simple" a high schooler could do it. I'm not sure that's the case for your standard fare high schooler, but I do presume that whatever means were used to prove the finiteness of Ramanujan-Nagell Squares and Triangular Numbers would come into play. Not being familiar with the ins and outs of unique factorization domains, which I know were involved in that proof, I look forward to any responses and have included complex expressions for terms that I see as being possibly related to the issue at hand...

Regarding notation and format:
A) I have included 0 and 1 terms (--> n (modulo 2) and/or additive and multiplicative identities) where appropriate to demonstrate similar form
B) I have also included leading zeroes, so that one may compare apples to apples reading "down" as well as left to right.

================================================================

THE RAMANUJAN-NAGELL TRIANGULAR (T_x) NUMBERS
{0,1,3,15,4095}
Z_1
------------------
4/2 * T_x = 2^y -2
--> (x^(2+0) - x^(0+0))/4

--> ((((x - 1)/2) - sqrt (-((x - 1)/2))) * (((x - 1)/2) + sqrt (-((x - 1)/2))) - 0*x)^(2/2) - 0*x)/1^2

A Simple Expression
(001^(2+0) - 001^(0+0))/4 = 0000 = 2/1*T_00 = 2^01 - 1
(003^(2+0) - 003^(0+0))/4 = 0002 = 2/1*T_01 = 2^02 - 1
(005^(2+0) - 005^(0+0))/4 = 0006 = 2/1*T_02 = 2^03 - 1
(011^(2+0) - 011^(0+0))/4 = 0030 = 2/1*T_05 = 2^05 - 1
(181^(2+0) - 181^(0+0))/4 = 8190 = 2/1*T_90 = 2^13 - 1

An Equivalent Complex Expression
((00 - sqrt (-00)) * (00 + sqrt (-00)) - 0)^(2/2) - 0)/1^2 = 0000 = 2/1*T_00 = 2^01 - 1
((01 - sqrt (-01)) * (01 + sqrt (-01)) - 0)^(2/2) - 0)/1^2 = 0002 = 2/1*T_01 = 2^02 - 1
((02 - sqrt (-02)) * (02 + sqrt (-02)) - 0)^(2/2) - 0)/1^2 = 0006 = 2/1*T_02 = 2^03 - 1
((05 - sqrt (-05)) * (05 + sqrt (-05)) - 0)^(2/2) - 0)/1^2 = 0030 = 2/1*T_05 = 2^05 - 1
((90 - sqrt (-90)) * (90 + sqrt (-90)) - 0)^(2/2) - 0)/1^2 = 8190 = 2/1*T_90 = 2^13 - 1

e.g.
((90 - sqrt (-90)) = 90 - 9.48683298 i
((90 + sqrt(-90)) = 90 + 9.48683298 iA ONE TO ONE RAMANUJAN-NAGELL TETRAHEDRAL (Tetra_x) COUNTERPART (?)
{0,0,4,20,84}
Z_2
------------------
3/2 * Tetra_(x-1) = 2^y -2
--> (x^(2+1) - x^(0+1))/4

--> ((((x - 0)/1) - sqrt (-((x - 0)/1))) * (((x - 0)/1) + sqrt (-((x - 0)/1))) - 1*x)^(3/2) - 1*x)/2^2

A Simple Expression
(000^(2+1) - 000^(0+1))/4 = 000 = 3/2 * Tetra_-1 = 2^1 - 1
(001^(2+1) - 000^(0+1))/4 = 000 = 3/2 * Tetra_0 = 2^1 - 1
(003^(2+1) - 003^(0+1))/4 = 006 = 3/2 * Tetra_2 = 2^3 - 1
(005^(2+1) - 005^(0+1))/4 = 030 = 3/2 * Tetra_4 = 2^5 - 1
(008^(2+1) - 008^(0+1))/4 = 126 = 3/2 * Tetra_7 = 2^7 - 1

An Equivalent Complex Expression
((00 - sqrt (-00)) * (00 + sqrt (-00)) - 0)^(3/2) - 0)/2^2 = 000 = 3/2 * Tetra_-1 = 2^1 - 1
((01 - sqrt (-01)) * (01 + sqrt (-01)) - 1)^(3/2) - 1)/2^2 = 000 = 3/2 * Tetra_0 = 2^1 - 1
((03 - sqrt (-03)) * (03 + sqrt (-03)) - 3)^(3/2) - 3)/2^2 = 006 = 3/2 * Tetra_2 = 2^3 - 1
((05 - sqrt (-05)) * (05 + sqrt (-05)) - 5)^(3/2) - 5)/2^2 = 030 = 3/2 * Tetra_4 = 2^5 - 1
((08 - sqrt (-08)) * (08 + sqrt (-08)) - 8)^(3/2) - 8)/2^2 = 126 = 3/2 * Tetra_7 = 2^7 - 1

e.g.
8 - sqrt(-8) = 8 - 2.82842712 i
8 + sqrt(-8) = 8 + 2.82842712 i

Z_0 = Z_1 UNION Z_2 (includes both 0's from Z_2, but no repeats between sets)
Z_0 --> {0,0,2,6,30,126,8190}
y_0 = y_1 UNION y_2
y_0 --> {1,1,2,3,5,7,13} --> n an element of N such that d'(p' - 1) = n

This set includes 1 repeated twice, plus the first 5 Mersenne Prime Exponents, the first 12 of which are...
{2,3,5,7,13,17,19,31,61,89,107,127...}

Background Note #1:
2,3,5,7, & 13 are the set of Mersenne Prime exponents highlighted by Frampton and Kephart in their 1999 paper:
Mersenne Primes, Polygonal Anomalies and String Theory Classification
http://arxiv.org/abs/hep-th/9904212

REASON FOR INTEREST:
If there is anything to the above conjecture, then this would bring me one step closer to building a reasonable case in support of an heuristically constructed hypothesis that predicts a 1:1 correspondence between "Frampton-Kephart" numbers and the Maximal Kissing Numbers of lattices in Dimension 1,4,8,14 and 24, with 1764 targeted as the Maximal Sphere Packing for Dimension 14 (126 * 14 = 1764).

e.g.
X_00 = 0000 * 00 = 000000 = K_00
X_00 = 0000 * 00 = 000000 = K_00
X_01 = 0002 * 01 = 000002 = K_01
X_04 = 0006 * 04 = 000024 = K_04
X_08 = 0030 * 08 = 000240 = K_08
X_14 = 0126 * 14 = 001764 = ?
X_24 = 8190 * 24 = 196560 = K_24

... for 0, 2, 6, 30 & 8190 constitute the elements of Z_1, (aka "Twice the Ramanujan-Nagell Triangular Numbers")

Background Note #2:
Z_1 INTERSECTION Z_2 = Z_0(-)
--> {0,6,30}

Let k = 3n + 1 --> {1, 4, 7}
Let x = (Z_0(-))^2 + (Z_0(-))^1 --> {0, 42, 930}
Then...
k*x = SUM [d(x)] for range (0,x)
Note: The Number of divisors of zero are considered to be 0

000 = 0^2 + 0
000 = ((0 - sqrt (-0)) * (0 + sqrt (-0)) - sqrt (-(0 - sqrt (-0)) * (0 + sqrt (-0)))) * ((0 - sqrt (-0)) * (0 + sqrt (-0)) + sqrt (-(0 - sqrt (-0)) * (0 + sqrt (-0))))
1*000 = 0000 = SUM [d(x)] for range n = 0 --> 000

042 = 6^2 + 6
042 = ((2 - sqrt (-2)) * (2 + sqrt (-2)) - sqrt (-(2 - sqrt (-2)) * (2 + sqrt (-2)))) * ((2 - sqrt (-2)) * (2 + sqrt (-2)) + sqrt (-(2 - sqrt (-2)) * (2 + sqrt (-2))))
4*042 = 0168 = SUM [d(x)] for range n = 0 --> 042

930 = 30^2 + 30
930 = ((5 - sqrt (-5)) * (5 + sqrt (-5)) - sqrt (-(5 - sqrt (-5)) * (5 + sqrt (-5)))) * ((5 - sqrt (-5)) * (5 + sqrt (-5)) + sqrt (-(5 - sqrt (-5)) * (5 + sqrt (-5))))
7*930 = 6510 = SUM [d(x)] for range n = 0 --> 930Related Sequence (extended to include 0):
Sum of divisor function d(n) (A000005) up to n is divisible by n
[0] 1, 4, 5, 15, 42, 44, 47, 121, 336, 340, 347, 930...
Sloane's A050226: http://www.research.att.com/~njas/sequences/A050226

Proper title for progression extension that includes 0:
Sum of divisor function d(n) (A000005) up to n is divisible by n!/|n-1|!

Background Note #3:
Conjecture 1.1 is a follow-up conjecture to...
CONJECTURE # 1.0
n an element of N such that d'(p' - 1) = n
n --> {0,1,2,3,4,6}
p' --> {1,2,3,5,7,13}
More: https://www.physicsforums.com/showthread.php?t=442527
 
Last edited by a moderator:
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Raphie said:
No x > 8, for x an element of N, satisfies the following equivalency: 3/2 * Tetra_(x-1) = 2^y -2 for any y an element of N

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for Tetra_x is the x-th Tetrahedral Number --> (n*(n+1)*(n+2))/3!

So, in short: there is no n > 7 where n^3 + 3n^2 + 2n + 8 is a power of two.

Raphie said:
This Conjecture has been computer checked to 100,000,000

I can far exceed that, since the power of two grows so quickly and the left side is monotonic. I just checked it to
Code:
141,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000
and that only took 12.7 seconds of computer time (though, admittedly, it took 10 minutes to code the test).

Raphie said:
it is so "simple" a high schooler could do it. I'm not sure that's the case for your standard fare high schooler, but I do presume that whatever means were used to prove the finiteness of Ramanujan-Nagell Squares and Triangular Numbers would come into play. Not being familiar with the ins and outs of unique factorization domains, which I know were involved in that proof, I look forward to any responses and have included complex expressions for terms that I see as being possibly related to the issue at hand...

High-school students don't understand UFDs (they're not introduced until an undergraduate algebra course), so it this is provable at that level the proof won't involve general properties of number fields and the like.

But it doesn't look like working mod small primes is useful here (how could they? there is a solution and hence modular solutions), and I don't know what other number theory techniques high-schoolers would have access to. The polynomial is irreducible, so that approach is out too.
 
Thanks, CRGreathouse. Did I count correctly in assuming you checked the result to 1.41*(10^1504)?

Another way to think of the formula in "simplest" terms from what you provided is:

(2+b)/2 * (1/4*(x^(2+b) - x^b)) = 2^y- 2

... for b = 0,1,0,1,0... = n (modulo 2)

Where b = 0, you get 2.0 times Ramanujan-Nagell Triangular Numbers for appropriate x and y
2.0 * (x^2 - x^0)/4 = 2^y - 2

Where b = 1, you get 1.5 times what I term, lacking any other appropriate expression, "Thoth Tetrahedral Numbers" for appropriate x & y
1.5 * (x^3 - x^1)/4 = 2^y - 2

(Note: If continued as a "steady" sequence of progressions, the next logical equation in the series would be... 1.0 * (x^4 - x^2)/4 = 2^y - 2; x Solutions --> 0, 1 and no other?)

This, I believe, better shows how Triangular numbers and Tetrahedral Numbers are related not only to the 2^y - 2 form, but to one another. (Tetrahedral Numbers, for those unawares, can be thought of most simply as the summation of the triangular numbers: 0 + 1 + 3 + 6 + 10...)

Also, apologies for the "mind typo" in the presentation of the numbers. 2^y - 1 should have read 2^y - 2, an equation form that is associated with...

Sphere Line Picking
Pick two points at random on a unit sphere. The first one can be placed at the north pole, i.e., assigned the coordinate (0, 0, 1), without loss of generality. The second point is then chosen at random using sphere point picking...
More: http://mathworld.wolfram.com/SphereLinePicking.html

I have edited this within the context of the quote provided below...Raphie

Raphie said:
[Edit] TYPO CORRECTION: 2^y -1 --> 2^y - 2[/Edit]

THE RAMANUJAN-NAGELL TRIANGULAR (T_x) NUMBERS
{0,1,3,15,4095}
Z_1
------------------
4/2 * T_x = 2^y -2
--> (x^(2+0) - x^(0+0))/4

--> ((((x - 1)/2) - sqrt (-((x - 1)/2))) * (((x - 1)/2) + sqrt (-((x - 1)/2))) - 0*x)^(2/2) - 0*x)/1^2

A Simple Expression
(001^(2+0) - 001^(0+0))/4 = 0000 = 2/1*T_00 = 2^01 - 2
(003^(2+0) - 003^(0+0))/4 = 0002 = 2/1*T_01 = 2^02 - 2
(005^(2+0) - 005^(0+0))/4 = 0006 = 2/1*T_02 = 2^03 - 2
(011^(2+0) - 011^(0+0))/4 = 0030 = 2/1*T_05 = 2^05 - 2
(181^(2+0) - 181^(0+0))/4 = 8190 = 2/1*T_90 = 2^13 - 2

An Equivalent Complex Expression
((00 - sqrt (-00)) * (00 + sqrt (-00)) - 0)^(2/2) - 0)/1^2 = 0000 = 2/1*T_00 = 2^01 - 2
((01 - sqrt (-01)) * (01 + sqrt (-01)) - 0)^(2/2) - 0)/1^2 = 0002 = 2/1*T_01 = 2^02 - 2
((02 - sqrt (-02)) * (02 + sqrt (-02)) - 0)^(2/2) - 0)/1^2 = 0006 = 2/1*T_02 = 2^03 - 2
((05 - sqrt (-05)) * (05 + sqrt (-05)) - 0)^(2/2) - 0)/1^2 = 0030 = 2/1*T_05 = 2^05 - 2
((90 - sqrt (-90)) * (90 + sqrt (-90)) - 0)^(2/2) - 0)/1^2 = 8190 = 2/1*T_90 = 2^13 - 2

e.g.
((90 - sqrt (-90)) = 90 - 9.48683298 i
((90 + sqrt(-90)) = 90 + 9.48683298 iA ONE TO ONE RAMANUJAN-NAGELL TETRAHEDRAL (Tetra_x) COUNTERPART (?)
{0,0,4,20,84}
Z_2
------------------
3/2 * Tetra_(x-1) = 2^y -2
--> (x^(2+1) - x^(0+1))/4

--> ((((x - 0)/1) - sqrt (-((x - 0)/1))) * (((x - 0)/1) + sqrt (-((x - 0)/1))) - 1*x)^(3/2) - 1*x)/2^2

A Simple Expression
(000^(2+1) - 000^(0+1))/4 = 000 = 3/2 * Tetra_-1 = 2^1 - 2
(001^(2+1) - 000^(0+1))/4 = 000 = 3/2 * Tetra_0 = 2^1 - 2
(003^(2+1) - 003^(0+1))/4 = 006 = 3/2 * Tetra_2 = 2^3 - 2
(005^(2+1) - 005^(0+1))/4 = 030 = 3/2 * Tetra_4 = 2^5 - 2
(008^(2+1) - 008^(0+1))/4 = 126 = 3/2 * Tetra_7 = 2^7 - 2

An Equivalent Complex Expression
((00 - sqrt (-00)) * (00 + sqrt (-00)) - 0)^(3/2) - 0)/2^2 = 000 = 3/2 * Tetra_-1 = 2^1 - 2
((01 - sqrt (-01)) * (01 + sqrt (-01)) - 1)^(3/2) - 1)/2^2 = 000 = 3/2 * Tetra_0 = 2^1 - 2
((03 - sqrt (-03)) * (03 + sqrt (-03)) - 3)^(3/2) - 3)/2^2 = 006 = 3/2 * Tetra_2 = 2^3 - 2
((05 - sqrt (-05)) * (05 + sqrt (-05)) - 5)^(3/2) - 5)/2^2 = 030 = 3/2 * Tetra_4 = 2^5 - 2
((08 - sqrt (-08)) * (08 + sqrt (-08)) - 8)^(3/2) - 8)/2^2 = 126 = 3/2 * Tetra_7 = 2^7 - 2

e.g.
8 - sqrt(-8) = 8 - 2.82842712 i
8 + sqrt(-8) = 8 + 2.82842712 i

Z_0 = Z_1 UNION Z_2 (includes both 0's from Z_2, but no repeats between sets)
Z_0 --> {0,0,2,6,30,126,8190}
y_0 = y_1 UNION y_2
y_0 --> {1,1,2,3,5,7,13} --> n an element of N such that d'(p' - 1) = n
 
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Raphie said:
Thanks, CRGreathouse. Did I count correctly in assuming you checked the result to 1.41*(10^1504)?

Should be 1.41e1505. This is, of course, a(n approximate) power of two.

Raphie said:
Another way to think of the formula in "simplest" terms from what you provided is:

(2+b)/2 * (1/4*(x^(2+b) - x^b)) = 2^y- 2

... for b = 0,1,0,1,0... = n (modulo 2)

That seems still complex -- more terms, more variables. Mine is "cubic equation in one variable is a power of two". It may be an interesting stating point for generalizations, though.
 
CRGreathouse said:
Should be 1.41e1505. This is, of course, a(n approximate) power of two.

That seems still complex -- more terms, more variables. Mine is "cubic equation in one variable is a power of two". It may be an interesting stating point for generalizations, though.

I agree with you CRGreathouse that it is more complex, but it also conveys, IMHO, more meaningful information, at least in relation to lattices. A few related facts about Tetrahedral Numbers from Wikipedia...

------------------------------------------------
The infinite sum of their reciprocals is 3/2

The tetrahedron with basic length 4 (summing up to 20) can be looked at as the 3-dimensional analogue of the tetractys, the 4th triangular number (summing up to 10).

When order-n tetrahedra built from T_n spheres are used as a unit, it can be shown that a space tiling with such units can achieve a densest sphere packing as long as n ≤ 4
------------------------------------------------
more: http://en.wikipedia.org/wiki/Tetrahedral_number

Also via Wikipedia, Tetra_1,3,8,20,34 are the only Tetrahedral numbers that are also triangular, and I wouldn't be much surprised if they can be rationally linked in 1:1 manner with the 0,1,2,3,4,6 and the 1,2,3,5,7,13 progressions I have recently posted in relation to.

By the way, I came across a really nice relationship in regards to those 3 facts posted up above. If you divide a ten element triangle into parts: Point (P), Triangle (T) and Hexagon (H) thusly...

0 0 0 T 0 0 0
0 0 H 0 H 0 0
0 H 0 P 0 H 0
T 0 H 0 H 0 T

... it becomes a simple matter, descriptively speaking, to derive the maximal known Kissing Numbers, divided by dimension, that are associated with Dimensions 1 through 10. One formula gives you the Union of P & T, while another (alternating) formula gives you H.

Most "simply," meaning in a manner that best preserves communication of the symmetrical relationships I wish to convey, while being as compact as possible, it can be expressed:

For m --> 1,1,2,2,3,3...
and a --> n+1 (modulo 2)

Then...

H_n = (2 + m!)^2*a - 2*(3/2*Tetra_m)*(-1)^(a+1)

H_ 1 = 3^2 - 3*1 = 6
H_ 2 = 0 + 3*1 = 3
H_ 3 = 4^2 - 3*4 = 4
H_ 4 = 0 + 3*4 = 12
H_ 5 = 8^2 - 3*10 = 34
H_ 6 = 0 + 3*10 = 30

P Union T = 2*(2*m^a - a)^2

2 * (2 - 1)^2 = 2
2 * (2 - 0)^2 = 8
2 * (4 - 1)^2 = 18
2 * (2 - 0)^2 = 8
2 * (6 - 1)^2 = 50
2 * (2 - 0)^2 = 8

Strip out repeats, arrange the two sets by value as an ordered set, then multiply by n and, voila...

02 * 01 = 002 = K_01*
03 * 02 = 006 = K_02*
04 * 03 = 012 = K_03*
06 * 04 = 024 = K_04*
08 * 05 = 040 = K_05
12 * 06 = 072 = K_06
18 * 07 = 126 = K_07
30 * 08 = 240 = K_08*
34 * 09 = 306 = K_09
50 * 10 = 500 = K_10
* Denotes proven Maximal Kissing Number (Lattice or non-Lattice Variety)

002
003 004
006 008 012
018 030 034 050

*

001
002 003
004 005 006
007 008 009 010

=

002
006 012
024 040 72
126 240 306 500

The Values associated...

P_n = 08
T_n = 02, 18, 50
H_n = 06, 03, 04, 12, 34, 30

... I might add, can all be related to the Fibonacci Series via summation, and T_n, in particular, can be related to the Central Binomial Coefficients 2, 20 & 70, 2 also being the square of the covering radius of the Leech Lattice and 70 being the square root of the sum of squares of the first 24 integers (i.e. the z coordinate of the Leech Lattice, or alternatively, the sum of the a + z coordinates, 0 & 70).Raphie

About the Tetractys...
http://en.wikipedia.org/wiki/Tetractys
 
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