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 A226915 #3 Jun 22 2013 10:57:10 %S A226915 -1,1,1,1,1,-1,3,-1,1,1,1,-1,3,-1,1,1,-1,3,3,1,1,1,3,-1,1,1,1,1,1,1,1, %T A226915 -1,-1,1,1,-1,3,-1,1,1,3,3,-1,1,-1,1,1,1,1,3,3,1,1,3,-1,1,1,1,-1,-1, %U A226915 -1,3,3,-1,-1,3,1,1,1,3,1,1,-1,3,-1,1,1,3,1,1,3,3,1,1,1,3,-1,1,1,3,1,1,-1,3,-1,1 %N A226915 Fourth column of A226518. %F A226915 a(n) = 1 + Legendre(2,p) + Legendre(3,p) where p = prime(n). %Y A226915 Cf. A226518. %K A226915 sign %O A226915 3,7 %A A226915 _N. J. A. Sloane_, Jun 22 2013