G.f.: Sum_{k>=0} x^(k*(k+1)) * Product_{j=1..k} 1/(1 - x^j)^3.

Terms

a(0) =1a(1) =0a(2) =1a(3) =3a(4) =6a(5) =10a(6) =16a(7) =24a(8) =37a(9) =55a(10) =84a(11) =124a(12) =186a(13) =270a(14) =394a(15) =561a(16) =798a(17) =1114a(18) =1553a(19) =2133a(20) =2924a(21) =3966a(22) =5364a(23) =7196a(24) =9629a(25) =12795a(26) =16956a(27) =22344a(28) =29355a(29) =38377