G.f.: Product_{k>=1} (1+x^k)^(3*k+2).

Terms

a(0) =1a(1) =5a(2) =18a(3) =61a(4) =182a(5) =506a(6) =1338a(7) =3369a(8) =8172a(9) =19197a(10) =43833a(11) =97636a(12) =212748a(13) =454461a(14) =953505a(15) =1968095a(16) =4001627a(17) =8024295a(18) =15885484a(19) =31074351a(20) =60111277a(21) =115071431a(22) =218126868a(23) =409662895a(24) =762679151a(25) =1408172844a(26) =2579599582a(27) =4690277001a(28) =8467363674a(29) =15182486586