%I A052856
%S A052856 1,2,4,14,76,542,4684,47294,545836,7087262,102247564,1622632574,
%T A052856 28091567596,526858348382,10641342970444,230283190977854,
%U A052856 5315654681981356,130370767029135902,3385534663256845324
%N A052856 A simple grammar.
%C A052856 Stirling transform of A005212(n-1)=[1,1,0,6,0,120,0,...] is a(n-1)=[1,
               2,4,14,76,...]. - Michael Somos Mar 04 2004
%C A052856 Stirling transform of (-1)^n*A052612(n-1)=[0,2,-2,12,-24,...] is a(n-1)=[0,
               2,4,14,76,...]. - Michael Somos Mar 04 2004
%C A052856 Stirling transform of A000142(n)=[2,2,6,24,120,...] is a(n)=[2,2,4,14,
               76,...]. - Michael Somos Mar 04 2004
%H A052856 INRIA Algorithms Project, <a href="http://algo.inria.fr/bin/encyclopedia?Search=ECSnb&argsearch=824">
               Encyclopedia of Combinatorial Structures 824</a>
%F A052856 E.g.f.: (1-3*exp(x)+exp(x)^2)/(-2+exp(x))
%p A052856 spec := [S,{B=Sequence(C),C=Set(Z,1 <= card),S=Union(B,C)},labeled]: 
               seq(combstruct[count](spec,size=n), n=0..20);
%o A052856 (PARI) a(n)=if(n<0,0,n!*polcoeff(subst(y+1/(1-y),y,exp(x+x*O(x^n))-1),
               n))
%Y A052856 A000670(n)=a(n)-1, if n>0. A032109(n)=a(n)/2, if n>0.
%Y A052856 Sequence in context: A032147 A007712 A075098 this_sequence A093462 A032052 
               A005737
%Y A052856 Adjacent sequences: A052853 A052854 A052855 this_sequence A052857 A052858 
               A052859
%K A052856 easy,nonn
%O A052856 0,2
%A A052856 encyclopedia(AT)pommard.inria.fr, Jan 25 2000