G.f. A(x) satisfies Sum_{n>=1} A(x^n - x^(n+1)) = x + x^2.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =12a(5) =34a(6) =108a(7) =350a(8) =1170a(9) =3980a(10) =13776a(11) =48286a(12) =171124a(13) =611994a(14) =2206018a(15) =8006120a(16) =29229932a(17) =107280390a(18) =395593940a(19) =1464883654a(20) =5445038132a(21) =20308989646a(22) =75985676050a(23) =285111556728