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

Terms

a(0) =0a(1) =1a(2) =3a(3) =5a(4) =9a(5) =13a(6) =20a(7) =28a(8) =39a(9) =54a(10) =71a(11) =94a(12) =124a(13) =159a(14) =201a(15) =258a(16) =322a(17) =401a(18) =499a(19) =613a(20) =750a(21) =918a(22) =1110a(23) =1340a(24) =1617a(25) =1935a(26) =2308a(27) =2752a(28) =3261a(29) =3854