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 A058371 #9 Feb 23 2019 21:33:40
%S A058371 0,0,1,3,12,48,217,1005,4878,24218,123021,634995,3323963,17596131,
%T A058371 94053675,506865965,2751093957,15025119759,82511460766,455331632088,
%U A058371 2523688452540,14042621802676,78415665739800,439298161502112,2468288819015277
%N A058371 The sequence S defined in A058540.
%p A058371 spec := [ S, {N=Union(Z,S,P,Q), S=Set(Union(Z,P,Q),card>=2), P=Set(Union(Z,S,Q),card>=2), Q=Set(Union(Z,S,P),card>=2)} ]; [seq(combstruct[count](spec,size=n), n=0..40)]; # N=A058540, S=A058371
%p A058371 spec:=[S,{S=Set(Union(Z,S,S),card>=2)}];[seq(combstruct[count](spec,size=n),n=0..25)]; # _Vladeta Jovovic_, Jun 25 2007
%Y A058371 Cf. A058575.
%K A058371 nonn
%O A058371 0,4
%A A058371 _N. J. A. Sloane_, Dec 26 2000