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

Terms

a(0) =1a(1) =1a(2) =4a(3) =6a(4) =15a(5) =22a(6) =48a(7) =75a(8) =137a(9) =218a(10) =384a(11) =593a(12) =1003a(13) =1549a(14) =2501a(15) =3857a(16) =6110a(17) =9256a(18) =14408a(19) =21675a(20) =33081a(21) =49422a(22) =74483a(23) =110135a(24) =164116a(25) =240955a(26) =355027a(27) =517553a(28) =755893a(29) =1093649