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 A052891 #16 Aug 10 2020 02:00:34
%S A052891 0,1,2,5,16,56,217,876,3686,15903,70103,314042,1426076,6548060,
%T A052891 30352695,141837086,667469159,3160370217,15045244375,71970393570,
%U A052891 345766441537,1667629158127,8071308125136,39190243658297,190845259909328,931856232714004,4561292365652751
%N A052891 Number of objects generated by the Combstruct grammar defined in the Maple program. See the link for the grammar specification.
%H A052891 Andrew Howroyd, <a href="/A052891/b052891.txt">Table of n, a(n) for n = 0..200</a>
%H A052891 INRIA Algorithms Project, <a href="http://ecs.inria.fr/services/structure?nbr=867">Encyclopedia of Combinatorial Structures 867</a>
%H A052891 Maplesoft, <a href="https://www.maplesoft.com/support/help/Maple/view.aspx?path=examples%2fcombstruct_grammars">Combstruct grammars</a>.
%F A052891 G.f.: 1 - 1/g(x) where g(x) is the g.f. of A052893. - _Andrew Howroyd_, Aug 09 2020
%p A052891 spec := [S, {C=Prod(Z,B), S=Set(C,1 <= card), B=Sequence(S)}, unlabeled]:
%p A052891 seq(combstruct[count](spec,size=n), n=0..20);
%o A052891 (PARI) EulerT(v)={Vec(exp(x*Ser(dirmul(v,vector(#v,n,1/n))))-1, -#v)}
%o A052891 seq(n)={my(v=[0]); for(n=1, n, v=concat([0],EulerT(Vec(1/(1-Ser(v)))))); v} \\ _Andrew Howroyd_, Aug 09 2020
%Y A052891 Cf. A052893.
%K A052891 easy,nonn
%O A052891 0,3
%A A052891 encyclopedia(AT)pommard.inria.fr, Jan 25 2000
%E A052891 Terms a(21) and beyond from _Andrew Howroyd_, Aug 09 2020