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 A052896 #26 Nov 20 2017 23:23:11
%S A052896 0,0,2,12,64,350,2024,12460,81638,567888,4180848,32470834,265219332,
%T A052896 2271692124,20350705418,190216812260,1850993707960,18714559108142,
%U A052896 196237054861920,2130518566431620,23912733627261670,277078872201375976,3310142647325149512
%N A052896 E.g.f.: (exp(exp(x)-1)-1)^2.
%C A052896 Previous name was: A simple grammar.
%C A052896 a(n) is the number of ways to place n labeled balls into unlabeled (but two-colored) boxes so that at least one box is red and one box is blue. - _Geoffrey Critzer_, Oct 16 2011
%H A052896 INRIA Algorithms Project, <a href="http://ecs.inria.fr/services/structure?nbr=872">Encyclopedia of Combinatorial Structures 872</a>
%F A052896 E.g.f.: exp(exp(x)-1)^2 - 2*exp(exp(x)-1) + 1.
%F A052896 For n >= 1: a(n) = Sum_{k=0...n} Stirling2(n,k)*(2^k-2) where Stirling2(n,k) is the number of set partitions of {1,2,...,n} into exactly k blocks (A008277).
%p A052896 spec := [S,{B=Set(Z,1 <= card),C=Set(B,1 <= card),S=Prod(C,C)},labeled]: seq(combstruct[count](spec,size=n), n=0..20);
%t A052896 a=Exp[Exp[x]-1]; Range[0,20]! CoefficientList[Series[(a-1)^2,{x,0,20}],x]
%Y A052896 Equals twice A000558.
%Y A052896 Cf. A001861, A008277.
%K A052896 easy,nonn
%O A052896 0,3
%A A052896 encyclopedia(AT)pommard.inria.fr, Jan 25 2000
%E A052896 New name using e.g.f., _Vaclav Kotesovec_, Nov 20 2017