G.f.: Product_{n>0} ( (1+x^n)/(1-x^n) )^(n^3).

Terms

a(0) =1a(1) =2a(2) =18a(3) =88a(4) =398a(5) =1768a(6) =7508a(7) =30644a(8) =121310a(9) =467234a(10) =1756080a(11) =6457168a(12) =23274788a(13) =82381584a(14) =286760344a(15) =982874120a(16) =3320800590a(17) =11070619228a(18) =36446345198a(19) =118581503192a(20) =381552358872