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

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =4a(5) =6a(6) =9a(7) =12a(8) =16a(9) =22a(10) =28a(11) =37a(12) =49a(13) =62a(14) =79a(15) =101a(16) =125a(17) =157a(18) =196a(19) =241a(20) =297a(21) =365a(22) =443a(23) =539a(24) =654a(25) =787a(26) =947a(27) =1137a(28) =1355a(29) =1616