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

Terms

a(0) =0a(1) =1a(2) =1a(3) =0a(4) =1a(5) =3a(6) =6a(7) =11a(8) =23a(9) =60a(10) =179a(11) =553a(12) =1716a(13) =5415a(14) =17801a(15) =61956a(16) =228391a(17) =882309a(18) =3530322a(19) =14531621a(20) =61454091a(21) =267479778a(22) =1200680113a(23) =5561767211a(24) =26553471186a(25) =130366882251a(26) =656668581417