G.f. A(x) satisfies -x = Product_{n>=1} (1 - x^n/A(x)) * (1 - x^(n-1)*A(x)) * (1 + x^n).

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =5a(5) =14a(6) =31a(7) =85a(8) =214a(9) =589a(10) =1572a(11) =4385a(12) =12124a(13) =34315a(14) =97006a(15) =277958a(16) =797969a(17) =2310313a(18) =6708311a(19) =19590928a(20) =57386238a(21) =168805975a(22) =497956135a(23) =1473704926a(24) =4372436946a(25) =13007158125a(26) =38779605810a(27) =115872525324a(28) =346897113802