G.f.: (1+x)/Product_{m>0} (1 - x^m).

Terms

a(0) =1a(1) =2a(2) =3a(3) =5a(4) =8a(5) =12a(6) =18a(7) =26a(8) =37a(9) =52a(10) =72a(11) =98a(12) =133a(13) =178a(14) =236a(15) =311a(16) =407a(17) =528a(18) =682a(19) =875a(20) =1117a(21) =1419a(22) =1794a(23) =2257a(24) =2830a(25) =3533a(26) =4394a(27) =5446a(28) =6728a(29) =8283