A225787 - OEIS

%I #4 May 16 2013 02:05:09

%S 2,3,2,11,19,3,5,0,71,23,109,131,17,181,2,239,271,307,0,379,3,13,127,

%T 61,67,163,701,47,811,97,37,991,0,31,0,79,83,0,41,7,0,191,37,0,5,83,

%U 541,251,2351,613,71,0,0,2861,743,3079,3191,367,0,3539,229,0,977,0,4159

%N Least prime number p such that p*triangular(n) is a triangular number, or 0 if no such p exists.

%F a(n) <= n^2 + n + 2.  For n>0, a(n) <= n^n + n + 1.

%e Least prime p such that triangular(3)*p is a triangular number is p=11, so a(3) = 11.

%Y Cf. A000217, A068084, A225502.

%K nonn

%O 0,1

%A _Alex Ratushnyak_, May 16 2013