G.f. satisfies: A(x) = (1 + x*A(x))*(1 + x^2*A(x)^3 + x^3*A(x)^4).

Terms

a(0) =1a(1) =1a(2) =2a(3) =7a(4) =25a(5) =92a(6) =359a(7) =1453a(8) =6018a(9) =25411a(10) =109032a(11) =473942a(12) =2082550a(13) =9235675a(14) =41284297a(15) =185819487a(16) =841433773a(17) =3830604764a(18) =17521832924a(19) =80490034307a(20) =371169646860