A Question to Trouble Even the Best of You


by adityab88
Tags: trouble
DaveC426913
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#19
Apr12-07, 10:12 PM
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What is an "arithmetical sequence"?
Data
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#20
Apr12-07, 10:20 PM
P: 998
An arithmetic sequence is one of the form [itex](n,n+k,n+2k,n+3k,...,n+mk,...)[/itex].
tehno
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#21
Apr13-07, 12:53 PM
P: 363
Quote Quote by Data View Post
About five seconds . It makes sense to start at 7; if you can find a sequence starting with 7 that has spacing smaller than 210 (and there's no smaller sequence starting with 7), then that's obviously the smallest one.
Ah,yes,yes,...
To me it makes sense to start with 199 and find "minimum" prime-sequence of 10 terms with spacing 210 :

[tex]
199, 409, 619, 829, 1039, 1249, 1459, 1669, 1879, 2089 [/tex].

But it took me longer time ,about 10 seconds
Edgardo
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#22
Apr13-07, 01:02 PM
P: 685
Quote Quote by DaveC426913 View Post
What is an "arithmetical sequence"?
I've written a mini-introduction to arithmetic progressions here
mr200backstrok
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#23
Apr13-07, 11:49 PM
P: 27
what about 31,41,51,61,71,81,91 ?

are there any non-primes in there?

but even if that is right (i doubt it is, i'm too tired to see the factors i probably should) i cheated b/c i guessed
d_leet
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#24
Apr13-07, 11:58 PM
P: 1,076
Quote Quote by mr200backstrok View Post
what about 31,41,51,61,71,81,91 ?

are there any non-primes in there?

but even if that is right (i doubt it is, i'm too tired to see the factors i probably should) i cheated b/c i guessed
51 and 81 are both composite.
mr200backstrok
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#25
Apr14-07, 12:01 AM
P: 27
oh

haha 9*9 = 81 yep im tired

Any idea where i could get a description of the concepts they are talking about? (I don't want to hijack the thread)
Data
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#26
Apr14-07, 12:24 AM
P: 998
Quote Quote by mr200backstrok View Post
Any idea where i could get a description of the concepts they are talking about? (I don't want to hijack the thread)
All I used for this problem was a little bit of modular arithmetic.


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