Expansion of Product_{k>=1} (1 + 3*x^k).

Terms

a(0) =1a(1) =3a(2) =3a(3) =12a(4) =12a(5) =21a(6) =48a(7) =57a(8) =84a(9) =120a(10) =228a(11) =264a(12) =399a(13) =516a(14) =732a(15) =1119a(16) =1416a(17) =1884a(18) =2532a(19) =3324a(20) =4296a(21) =6168a(22) =7545a(23) =9984a(24) =12684a(25) =16500a(26) =20577a(27) =26688a(28) =34572a(29) =43032