This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A225787 #4 May 16 2013 02:05:09 %S A225787 2,3,2,11,19,3,5,0,71,23,109,131,17,181,2,239,271,307,0,379,3,13,127, %T A225787 61,67,163,701,47,811,97,37,991,0,31,0,79,83,0,41,7,0,191,37,0,5,83, %U A225787 541,251,2351,613,71,0,0,2861,743,3079,3191,367,0,3539,229,0,977,0,4159 %N A225787 Least prime number p such that p*triangular(n) is a triangular number, or 0 if no such p exists. %F A225787 a(n) <= n^2 + n + 2. For n>0, a(n) <= n^n + n + 1. %e A225787 Least prime p such that triangular(3)*p is a triangular number is p=11, so a(3) = 11. %Y A225787 Cf. A000217, A068084, A225502. %K A225787 nonn %O A225787 0,1 %A A225787 _Alex Ratushnyak_, May 16 2013