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 A318432 #20 Aug 28 2018 19:27:05
%S A318432 1,4,12,76,460,3104,22404,169152,1315020,10460416,84764512,697212652,
%T A318432 5805722692,48847196896,414623627136,3546272614976,30532934225100,
%U A318432 264420681260336,2301782759539392,20129523771781288,176765807152990560,1558058796052048968
%N A318432 Number of n-element subsets of [4n] whose elements sum to a multiple of n.
%H A318432 Marko Riedel et al., <a href="https://math.stackexchange.com/questions/2894653/">Number of n-element subsets divisible by n</a>
%F A318432 a(n) = (-1)^n * (1/n) * Sum_{d|n} C(4d,d)*(-1)^d*phi(n/d) for n>0, a(0)=1.
%p A318432 with(numtheory); a := n -> `if`(n=0, 1, (-1)^n * 1/n * add(binomial(4*d,d)*(-1)^d*phi(n/d), d in divisors(n)));
%o A318432 (PARI) a(n) = if (n, (-1)^n * (1/n) * sumdiv(n, d, binomial(4*d,d)*(-1)^d*eulerphi(n/d)), 1); \\ _Michel Marcus_, Aug 27 2018
%Y A318432 Cf. A169888, A318431, A318433.
%Y A318432 Column k=4 of A304482.
%K A318432 nonn
%O A318432 0,2
%A A318432 _Marko Riedel_, Aug 26 2018