G.f.: 1 + Sum_{n>=1} a(n)*x^n/(1 - x^n) = Product_{n>=1} (1 + x^n)/(1 - x^n).

Terms

a(0) =2a(1) =2a(2) =6a(3) =10a(4) =22a(5) =30a(6) =62a(7) =86a(8) =146a(9) =206a(10) =342a(11) =454a(12) =726a(13) =974a(14) =1442a(15) =1962a(16) =2862a(17) =3762a(18) =5398a(19) =7094a(20) =9834a(21) =12942a(22) =17726a(23) =22938a(24) =31042a(25) =40094a(26) =53254a(27) =68518a(28) =90246a(29) =114914