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 A068013 #6 Sep 08 2022 13:09:22
%S A068013 1,1,1,1,3,5,10,20,38,74,146,294,586,1172,2344,4684,9364,18724,37452,
%T A068013 74900,149800,299600,599192,1198376,2396744,4793496,9586984,19173968,
%U A068013 38347936,76695856,153391696,306783376,613566768,1227133520,2454267040
%N A068013 Number of subsets of {1,2,3,...,n} that sum to 0 mod 7.
%F A068013 Empirical G.f.: -(2*x^7+x^5-x^4+x^3+x^2+x-1) / ((2*x-1)*(2*x^7-1)). [_Colin Barker_, Dec 22 2012]
%Y A068013 7th row of A068009.
%K A068013 nonn
%O A068013 0,5
%A A068013 _Antti Karttunen_, Feb 11 2002