Weigh transform of A007561.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =4a(5) =10a(6) =26a(7) =71a(8) =197a(9) =564a(10) =1639a(11) =4833a(12) =14406a(13) =43374a(14) =131652a(15) =402525a(16) =1238419a(17) =3831520a(18) =11912913a(19) =37204431a(20) =116655147a(21) =367100319a(22) =1159026041a(23) =3670339794a(24) =11655070593a(25) =37104257405a(26) =118398974620a(27) =378627600346