A086340 - OEIS

%I #8 Jul 27 2013 12:51:22

%S 1,3,5,56

%N Numbers n such that 1 + (n-1)*n*(n+1) is a square.

%D M. Lambrou, Solution to problem 2411, Crux Mathematicorum, Feb. 2000 26(1) 59-60 CMS.

%o (PARI) isok(n) = issquare(1 + (n-1)*n*(n+1)) \\ _Michel Marcus_, Jul 27 2013

%K fini,nonn

%O 1,2

%A _Lekraj Beedassy_, Sep 02 2003