%I A052812
%S A052812 1,0,1,2,3,6,9,16,24,42,63,102,157,244,373,570,858,1290,1930,2858,4228,
%T A052812 6208,9084,13216,19175,27666,39804,57020,81412,115820,164264,232178,
%U A052812 327220,459796,644232,900214,1254554,1743896,2418071,3344896,4616026
%N A052812 A simple grammar: power set of pairs of sequences.
%C A052812 Number of partitions of n objects of two colors into distinct parts, 
               where each part must contain at least one of each color. - Franklin 
               T. Adams-Watters (FrankTAW(AT)Netscape.net), Dec 28 2006
%H A052812 INRIA Algorithms Project, <a href="http://algo.inria.fr/bin/encyclopedia?Search=ECSnb&argsearch=776">
               Encyclopedia of Combinatorial Structures 776</a>
%F A052812 G.f.: exp(Sum((-1)^(j[1]+1)*(x^j[1])^2/(x^j[1]-1)^2/j[1], j[1]=1 .. infinity))
%F A052812 G.f.: Product_{k>=1} (1+x^k)^(k-1). - Vladeta Jovovic (vladeta(AT)eunet.rs), 
               Sep 17 2002
%F A052812 Weigh transform of b(n) = n-1. - Franklin T. Adams-Watters (FrankTAW(AT)Netscape.net), 
               Dec 28 2006
%p A052812 spec := [S,{B=Sequence(Z,1 <= card),C=Prod(B,B),S= PowerSet(C)},unlabeled]: 
               seq(combstruct[count](spec,size=n), n=0..20);
%Y A052812 Cf. A052847.
%Y A052812 Sequence in context: A147227 A147063 A007865 this_sequence A062114 A094768 
               A093830
%Y A052812 Adjacent sequences: A052809 A052810 A052811 this_sequence A052813 A052814 
               A052815
%K A052812 easy,nonn
%O A052812 0,4
%A A052812 encyclopedia(AT)pommard.inria.fr, Jan 25 2000
%E A052812 More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), Sep 17 2002