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 A165573 #6 Mar 12 2017 12:10:45 %S A165573 0,1,1,-1,1,-1,-1,-1,1,1,-1,1,-1,1,-1,1,1,1,1,-1,-1,1,1,1,-1,1,1,-1, %T A165573 -1,1,1,1,1,-1,1,1,1,-1,-1,-1,-1,-1,1,-1,1,-1,1,-1,-1,1,1,-1,1,-1,-1, %U A165573 -1,-1,1,1,1,1,1,1,-1,1,-1,-1,1,1,-1,1,-1,1,1,-1,-1,-1,-1,-1,1,-1,1 %N A165573 Legendre symbol (n,257). %C A165573 257 is the 3rd Fermat prime, A019434(3). %H A165573 A. Karttunen, <a href="/A165573/b165573.txt">Table of n, a(n) for n = 0..257</a> %o A165573 (PARI) a(n) = kronecker(n, 257); \\ _Michel Marcus_, Mar 12 2017 %Y A165573 Partial sums: A165575. %K A165573 sign,mult %O A165573 0,1 %A A165573 _Antti Karttunen_, Sep 22 2009