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 A309297 #6 Jul 22 2019 08:59:04 %S A309297 0,0,0,1,4,12,29,71,186,468,1144,2718,6390,14920,34440,78720,178320, %T A309297 401088,896576,1992416,4404288,9689056,21223216,46305264,100663680, %U A309297 218104640,471104880,1014686160,2179696352,4670778048,9985801344,21303039648,45354855072 %N A309297 (1/5) times the sum of the elements of all subsets of [n] whose sum is divisible by five. %H A309297 Alois P. Heinz, <a href="/A309297/b309297.txt">Table of n, a(n) for n = 0..1000</a> %H A309297 <a href="/index/Rec#order_18">Index entries for linear recurrences with constant coefficients</a>, signature (6,-12,8,0,6,-36,72,-48,0,-12,72,-144,96,0,8,-48,96,-64). %F A309297 G.f.: -x^3*(8*x^13+16*x^10-12*x^9+16*x^6-6*x^5-9*x^4+3*x^3+2*x-1) / ((2*x-1)^3 *(2*x^5-1)^3). %Y A309297 Column k=5 of A309280. %K A309297 nonn,easy %O A309297 0,5 %A A309297 _Alois P. Heinz_, Jul 21 2019