G.f.: Sum_{n>=0} Product_{k=1..n} Series_Reversion( x/(1 + x^k) ).

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =5a(5) =7a(6) =12a(7) =17a(8) =29a(9) =44a(10) =77a(11) =114a(12) =218a(13) =330a(14) =617a(15) =987a(16) =1913a(17) =2968a(18) =6068a(19) =9500a(20) =19263a(21) =31399a(22) =64268a(23) =101702a(24) =218891a(25) =348559a(26) =735823a(27) =1205239a(28) =2576727a(29) =4119884