Find the smallest integer n that makes 11 x 14^n + 1, a prime number, or, prove that it doesn't exist.

Consider f(n) = 11 x 14^n + 1, modulo 15.
f(n) = 11 x (-1)^n + 1 = 12 or 5 (mod 15).
Hence f(n) = 0 (mod 3) or 0 (mod 5), is greater than 5 for all n, and is always composite.
Edited on June 9, 2005, 12:36 pm

Posted by Nick Hobson on 2005-06-09 12:30:05