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

Terms

a(0) =1a(1) =0a(2) =1a(3) =2a(4) =7a(5) =23a(6) =81a(7) =293a(8) =1087a(9) =4110a(10) =15783a(11) =61387a(12) =241329a(13) =957400a(14) =3828055a(15) =15410651a(16) =62410871a(17) =254095382a(18) =1039394147a(19) =4269718110a(20) =17606507789a(21) =72852976317a(22) =302403773303