G.f. 1/(1-sum(n=1,N,x^(n*(3*n-1)/2))).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =2a(6) =3a(7) =4a(8) =5a(9) =6a(10) =8a(11) =11a(12) =16a(13) =22a(14) =29a(15) =38a(16) =50a(17) =68a(18) =93a(19) =126a(20) =169a(21) =225a(22) =302a(23) =407a(24) =550a(25) =742a(26) =997a(27) =1339a(28) =1799a(29) =2421