G.f.: Product_{k>=1} (1 + x^k) / (1 - x^(k*(k+1)/2)).

Terms

a(0) =1a(1) =2a(2) =3a(3) =6a(4) =9a(5) =13a(6) =21a(7) =30a(8) =41a(9) =59a(10) =81a(11) =108a(12) =147a(13) =195a(14) =253a(15) =333a(16) =431a(17) =549a(18) =704a(19) =892a(20) =1119a(21) =1409a(22) =1758a(23) =2176a(24) =2697a(25) =3321a(26) =4065a(27) =4976a(28) =6061a(29) =7345