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 A177985 #6 Jun 15 2016 07:21:20 %S A177985 1,1,-2,4,1,-5,7,1,-8,10,-9,-1,13,1,-14,1,16,-17,19,1,-20,22,-20,-2, %T A177985 25,-24,-1,28,1,-29,1,31,-32,34,1,-35,2,36,-38,40,-39,-1,43,-41,-2,1, %U A177985 46,-47,49,1,-50,52,1,-53,55,-54,-1,2,2,-4,1,61,-62,64,-62,-2,67,1,-68,4,-3,-1,73,1,-74,1,76,-77,2,78 %N A177985 A177983(n) - A177961(n). %F A177985 a(3k+1)+a(3k+2)+a(3k+3)=0, k>=0. %Y A177985 Cf. A177983, A177961. %K A177985 sign,easy %O A177985 1,3 %A A177985 _Vladimir Shevelev_, May 16 2010