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 A127315 #7 Mar 31 2012 14:47:12
%S A127315 1,2,3,6,42,78,546,1806,23478
%N A127315 Numbers n such that n^4 divides 19^(n^2)-1.
%C A127315 a(n)^2 are the perfect squares in A128399.
%C A127315 a(10) > 10^13. [From Max Alekseyev]
%t A127315 Do[g=PowerMod[19,n^2,n^4]-1;If[IntegerQ[g/n^4],Print[n]],{n,1,10000}]
%Y A127315 Cf. A128399 = numbers n such that n^2 divides 19^n-1.
%K A127315 hard,more,nonn
%O A127315 1,2
%A A127315 _Alexander Adamchuk_, Mar 28 2007
%E A127315 a(9) from _D. S. McNeil_, Mar 02 2009