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

Terms

a(0) =1a(1) =3a(2) =10a(3) =28a(4) =72a(5) =172a(6) =397a(7) =867a(8) =1840a(9) =3783a(10) =7580a(11) =14829a(12) =28454a(13) =53540a(14) =99119a(15) =180676a(16) =324758a(17) =576145a(18) =1010051a(19) =1750782a(20) =3003386a(21) =5101769a(22) =8586891a(23) =14327582a(24) =23711567a(25) =38937304a(26) =63471475a(27) =102741924a(28) =165204561a(29) =263956121