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 A318591 #6 Aug 29 2018 17:48:20
%S A318591 1,1,5,30,165,1001,6198,38760,245157,1562331,10015005,64512240,
%T A318591 417226230,2707475148,17620076360,114955810530,751616304549,
%U A318591 4923689695575,32308782871911,212327989773900,1397281501935165,9206478467531865,60727722660586800,400978991944396320
%N A318591 Number of n-member subsets of [3*n] whose elements sum to a multiple of three.
%H A318591 Alois P. Heinz, <a href="/A318591/b318591.txt">Table of n, a(n) for n = 0..1000</a>
%e A318591 a(2) = 5: {1,2}, {1,5}, {2,4}, {3,6}, {4,5}.
%Y A318591 Column k=3 of A318557.
%K A318591 nonn
%O A318591 0,3
%A A318591 _Alois P. Heinz_, Aug 29 2018