Determine all possible values of a positive integer N ≥ 3, such that ^NC₂ – 1 is a prime power.

Note: ^NC₂ represents N choose 2.

(In reply to re: No Subject by farcear)

I was thinking of (n-2) and (n+1) which if neither is 1 and they produce a prime power must be each be powers of 3.

The actual factors [1] (.5n-1)(n+1) or [2] (n-2)(.5n+.5) can differ by any value.

This does not change much since exponents grow so fast that
2*p^x+3 = p^y
and
p^x = 2*p^y - 3

Only have solutions if p=3 anyway (p cannot be 2 due to the +3 or -3)

Posted by Jer on 2010-04-26 15:42:02