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

Terms

a(0) =1a(1) =3a(2) =11a(3) =31a(4) =85a(5) =209a(6) =504a(7) =1138a(8) =2514a(9) =5339a(10) =11098a(11) =22432a(12) =44535a(13) =86523a(14) =165496a(15) =311187a(16) =577190a(17) =1055524a(18) =1907423a(19) =3405574a(20) =6016826a(21) =10520065a(22) =18222215a(23) =31275320a(24) =53230224a(25) =89860112a(26) =150551503a(27) =250388180a(28) =413572707a(29) =678574627