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

Terms

a(0) =1a(1) =2a(2) =7a(3) =16a(4) =41a(5) =86a(6) =193a(7) =384a(8) =787a(9) =1504a(10) =2899a(11) =5338a(12) =9852a(13) =17586a(14) =31330a(15) =54490a(16) =94350a(17) =160370a(18) =271171a(19) =451776a(20) =748460a(21) =1225106a(22) =1993860a(23) =3212378a(24) =5146851a(25) =8175114a(26) =12915747a(27) =20252564a(28) =31595134a(29) =48964310