G.f. satisfies: A(x) = 1/(1 - x/A(-x*A(x)^4)).

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =20a(5) =76a(6) =313a(7) =1375a(8) =6337a(9) =30243a(10) =148129a(11) =739172a(12) =3737993a(13) =19077868a(14) =97955307a(15) =504707999a(16) =2604312205a(17) =13436676965a(18) =69229324721a(19) =355854322633