P is a positive integer such that each of 2P + 1 and 3P + 1 is a perfect square.

Prove that P is divisible by 40

(In reply to Two values, no proof by brianjn)

Using just the three terms you gave, Sloane's Integer Encyclopedia returned exactly one hit: A045502 "2n+1 and 3n+1 are squares"

The sequence continues with: 0, 40, 3960, 388080, 38027920, 3726348120, 365144087880, 35780394264160, ...

Posted by Brian Smith on 2008-05-14 12:26:42