G.f.: Product_{j>=1} Product_{i>=1} (1 + x^(i*j)).

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =6a(5) =10a(6) =17a(7) =25a(8) =38a(9) =59a(10) =86a(11) =125a(12) =184a(13) =260a(14) =369a(15) =524a(16) =726a(17) =1005a(18) =1391a(19) =1894a(20) =2576a(21) =3493a(22) =4687a(23) =6272a(24) =8373a(25) =11090a(26) =14647a(27) =19294a(28) =25265a(29) =32991