G.f.: Sum_{k>=0} x^(k*(k+1)/2) * Product_{j=1..k} 1/(1 - x^j)^4.

Terms

a(0) =1a(1) =1a(2) =4a(3) =11a(4) =24a(5) =49a(6) =93a(7) =173a(8) =310a(9) =549a(10) =946a(11) =1608a(12) =2676a(13) =4391a(14) =7083a(15) =11283a(16) =17724a(17) =27539a(18) =42309a(19) =64382a(20) =97052a(21) =145092a(22) =215161a(23) =316737a(24) =462980a(25) =672310a(26) =970154a(27) =1391667a(28) =1984999a(29) =2816059