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

Terms

a(0) =1a(1) =1a(2) =1a(3) =4a(4) =11a(5) =29a(6) =85a(7) =281a(8) =1003a(9) =3764a(10) =14811a(11) =61327a(12) =267153a(13) =1219497a(14) =5807473a(15) =28763988a(16) =147898511a(17) =788330533a(18) =4349414397a(19) =24799271517a(20) =145904796179a(21) =884577652276