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 A068031 #10 May 02 2025 15:36:04
%S A068031 1,1,1,1,2,4,7,13,26,52,104,206,410,820,1640,3280,6556,13108,26216,
%T A068031 52432,104864,209720,419432,838864,1677728,3355456,6710896,13421776,
%U A068031 26843552,53687104,107374208,214748384,429496736,858993472,1717986944,3435973888,6871947712
%N A068031 Number of subsets of {1,2,3,...,n} that sum to 0 mod 10.
%F A068031 Empirical G.f.: (x-1)*(2*x^7+3*x^6+4*x^5+2*x^4+2*x^3+x^2-1) / ((2*x-1)*(2*x^5-1)). - _Colin Barker_, Dec 22 2012
%p A068031 b:= proc(n, s) option remember; `if`(n=0, `if`(s=0, 1, 0),
%p A068031 b(n-1, s)+b(n-1, irem(s+n, 10)))
%p A068031 end:
%p A068031 a:= n-> b(n, 0):
%p A068031 seq(a(n), n=0..36); # _Alois P. Heinz_, May 02 2025
%Y A068031 10th row of A068009.
%K A068031 nonn
%O A068031 0,5
%A A068031 _Antti Karttunen_, Feb 11 2002