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 A055538 #8 Jul 02 2025 16:01:59
%S A055538 4,20,65,170,383,779,1470,2611,4418,7182,11283,17213,25601,37230,
%T A055538 53074,74327,102434,139133,186501,246988,323479,419344,538492,685438,
%U A055538 865376,1084236,1348777,1666664,2046551,2498179,3032482,3661673,4399374
%N A055538 Number of asymmetric types of (3,n)-hypergraphs without isolated nodes, under action of symmetric group S_3; asymmetric n-covers of an unlabeled 3-set.
%C A055538 Cover may include both empty sets and multiple occurrences of a subset.
%F A055538 G.f. : (1/(1-x)^8-3/(1-x)^4/(1-x^2)^2+2/(1-x)^2/(1-x^3)^2-3/(1-x)^4+3/(1-x)^2/(1-x^2)+6/(1-x)^2-6/(1-x))/6.
%e A055538 There are 4 asymmetric (3,3)-hypergraphs without isolated nodes: {{1,2},{1,2},{1,3}}, {{1},{1,2},{1,2,3}}, {{1},{1,2},{2,3}}, {{1},{2},{1,3}}.
%Y A055538 Cf. A005745.
%K A055538 nonn
%O A055538 3,1
%A A055538 _Vladeta Jovovic_, Jul 09 2000
%E A055538 More terms from _James Sellers_, Jul 11 2000