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 A117946 #5 May 29 2025 07:49:19
%S A117946 0,1,-2,0,2,-4,0,1,-2,0,2,-4,0,4,-8,0,2,-4,0,1,-2,0,2,-4,0,1,-2,0,2,
%T A117946 -4,0,4,-8,0,2,-4,0,4,-8,0,8,-16,0,4,-8,0,2,-4,0,4,-8,0,2,-4,0,1,-2,0,
%U A117946 2,-4,0,1,-2,0,2,-4,0,4,-8,0,2,-4,0,1,-2,0,2,-4,0,1,-2,0,2,-4,0,4,-8,0,2,-4,0,4,-8,0,8,-16,0,4,-8
%N A117946 a(3n)=0, a(3n+1)/a(1)=a(3n+2)/a(2)=A059151(n).
%C A117946 Second column of A117939.
%F A117946 a(n)=sum{k=0..n, L((n-k)/3)*L(C(n,k)/3)} where L(j/p) is the Legendre symbol of j and p.
%K A117946 easy,sign
%O A117946 0,3
%A A117946 _Paul Barry_, Apr 05 2006