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

Terms

a(0) =1a(1) =1a(2) =0a(3) =1a(4) =2a(5) =3a(6) =5a(7) =11a(8) =29a(9) =80a(10) =222a(11) =630a(12) =1881a(13) =6004a(14) =20420a(15) =72979a(16) =270659a(17) =1035590a(18) =4087205a(19) =16675630a(20) =70440641a(21) =307933393a(22) =1390117953a(23) =6462787357a(24) =30871458702a(25) =151298796000a(26) =760250325004