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 A089509 #23 Sep 08 2022 08:45:12
%S A089509 1,1,1,1,-1,1,0,1,1,-1,-1,1,-1,0,-1,1,-1,1,1,-1,0,-1,-1,1,1,-1,1,0,1,
%T A089509 -1,1,1,-1,-1,0,1,1,1,-1,-1,-1,0,-1,-1,-1,-1,1,1,0,1,-1,-1,1,1,1,0,1,
%U A089509 1,1,-1,-1,1,0,1,1,-1,-1,-1,-1,0,-1,1,-1,1,1,1,0,-1,-1,-1,1,-1,1,0,1,-1,1,-1,-1,-1,0,-1,1,1,-1,1,-1,0,-1,1,-1,-1,1,-1,0,1
%N A089509 a(n) = Kronecker(7/n).
%H A089509 Vincenzo Librandi, <a href="/A089509/b089509.txt">Table of n, a(n) for n = 1..1000</a>
%H A089509 Jean-Paul Allouche, Leo Goldmakher, <a href="http://arxiv.org/abs/1608.03957">Mock characters and the Kronecker symbol</a>, arXiv:1608.03957 [math.NT], 2016.
%F A089509 if n==0 (mod 7) a(n)=0; for p in=A003632 a(p)=-1; for p in A038878 a(p)=+1
%t A089509 Table[KroneckerSymbol[7, n], {n, 100}] (* _Vincenzo Librandi_, Aug 16 2016 *)
%o A089509 (PARI) a(n)=kronecker(7,n)
%o A089509 (Magma) [KroneckerSymbol(7,n): n in [1..100]]; // _Vincenzo Librandi_, Aug 16 2016
%Y A089509 Cf. A091338, A080891.
%K A089509 sign,mult
%O A089509 1,1
%A A089509 _Benoit Cloitre_, Jan 03 2004
%E A089509 Keyword:mult added by _Andrew Howroyd_, Jul 23 2018