Pythagorean triples:
http://grail.cba.csuohio.edu/~somos/rtritab.txt
The Fibonacci numbers are also within Pythagorean triples
a^2 + b^2 = c^2 .
15^2 + 8^2 = 17^2
35^2 +12^2 = 37^2
99^2 + 20^2 = 101^2
255^2 + 32^2 = 257^2
675^2 + 52^2 = 677^2
1763^2 + 84^2 = 1765^2
4623^2 + 136^2 = 4625^2
etc.
At closer inspection:
(4^2-1)^2 + (2*4)^2 = (4^2+1)^2
(6^2-1)^2 + (2*6)^2 = (6^2+1)^2
(10^2-1)^2 + (2*10)^2 = (10^2+1)^2
(16^2-1)^2 + (2*16)^2 = (16^2+1)^2
(26^2-1)^2 + (2*26)^2 = (26^2+1)^2
(42^2-1)^2 + (2*42)^2 = (42^2+1)^2
(68^2-1)^2 + (2*68)^2 = (68^2+1)^2
etc...
Notice:
4 = 2*2
6 = 2*3
10 = 2*5
16 = 2*8
26 = 2*13
42 = 2*21
68 = 2*34
2*Fibonacci
etc...
Interesting...
While researching "squares" of numbers I find that ratios of certain types of squares always involve something like a + (2b)^(1/2).
I found many squares that have successive ratios that tend towards the number
3 + (8)^(1/2)
This is of course one solution to the polynomial x^2 - 6x + 1 = 0.
The challenge is to answer the question "why"
are these squares ratios tending towards
3 + (8)^(1/2) as the numbers are getting larger?
I will give some "lists" of these squares!
3^2 + 4^2 = 5^2
20^2 + 21^2 = 29^2
119^2 + 120^2 = 169^2
696^2 + 697^2 = 985^2
4059^2 + 4060^2 = 5741^2
23660^2 + 23661^2 = 33461^2
137903^2 + 137904^2 = 195025^2
Now the ratios
29/5 = 5.8
169/29 = 5.827586207...
985/169 = 5.828402367...
5741/985 = 5.828426396...
33461/5741 = 5.828427103...
195025/33461 = 5.828427124...
3 + (8)^(1/2) = 5.828427125...
This number also appears for the successive ratios of any of the three numbers
(a, b, c), a2/a1, b2/b1, or c2/c1 of the Pythagorean triples on the above list.
Here are some more...
3 = 2^2 - 1
17 = 4^2 + 1
99 = 10^2 - 1
577 = 24^2 + 1
3363 = 58^2 - 1
19601 = 140^2 + 1
114243 = 338^2 - 1
665857 = 816^2 + 1
The ratios
17/3 = 5.666666667...
99/17 = 5.823529412...
577/99 = 5.828282828...
3363/577 = 5.828422877...
19601/3363 = 5.828427...
114243/19601 = 5.828427121...
665857/114243 = 5.828427125...
Also approaching 3 + (8)^(1/2)
The mathematicians tell me "no-problemo" an easy problem!
This is what one mathematician explained to me...
Hi, this is easy to explain.
Notice that your equation is basically of the form
a^2 + (a+1)^2 + 1 = b^2
Never mind, for the moment, that you are considering consecutive ratios of b. First start by trying to understand which a's and b's can be solutions to this equation.
Well, this equation is the same as:
2a^2 + 2a + 1 - b^2 = 0.
Which is the same as
4a^2 + 4a + 2 - 2b^2 = 0
which is
(2a+1)^2 -2b^2 = -1
This is a special case of Pell's Equation
X^2 - 2Y^2 = -1 (i.e. where X=2a+1 and Y=b).
Now observe that (X,Y) = (1,1) is a solution.
It turns out that all the solutions
(X_k, Y_k) to this equation are given by
X_k + sqrt(2) Y_k = (1+sqrt(2))^k where k is odd.
Now your question relates to those X_k which are odd. Now compute some examples with k = 1,3,5,7,9,11,13... you will see a pattern. This explains your observations.
1+sqrt2)^2 = (3 + sqrt8)
(1+sqrt2)^3 = (7 + sqrt50)
(1+sqrt2)^4 = (17 + sqrt288)
(1+sqrt2)^5 = (41 + sqrt1682)
(1+sqrt2)^6 = (99 + sqrt9800)
(1+sqrt2)^7 = (239 + sqrt57122)
(1+sqrt2)^8 = (577 + sqrt332928)
The Fibonacci sequence:
1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144,
233...
1+0 = 1
1+1 = 2
1+2 = 3
2+3 = 5
3+5 = 8
5+8 = 13
8+13 = 21
etc...
Fibonacci squares... also generate Fibonacci numbers...
1^2 - 0^2 = 1
1^2 + 1^2 = 2
2^2 - 1^2 = 3
2^2 + 1^2 = 5
3^2 - 1^2 = 8
3^2 + 2^2 = 13
5^2 - 2^2 = 21
5^2 + 3^2 = 34
8^2 - 3^2 = 55
8^2 + 5^2 = 89
13^2 - 5^2 = 144
13^2 + 8^2 = 233
21^2 -8^2 = 377
21^2 + 13^2 = 610
etc...
The consecutive ratios of these numbers... are of course approaching (1 + sqrt(5))/2
The "golden" ratio...
Sum the digits of 2^n and get a repeating pattern:
2^1 = 2
2^2 = 4
2^3 = 8
2^4 = 16, 1+6 = 7
2^5 = 32, 3+2 = 5
2^6 = 64, 6+4 = 10, 1+0 = 1
2^7 ---> 2
2^8 ---> 4
2^9 ---> 8
2^10 ---> 7
2^11 ---> 5
2^12 ---> 1
2^13 ---> 2
2^14 ---> 4
etc...
etc...
etc...