Expansion of Sum_{k>=0} x^(k*(k+1)/2) * Product_{j=1..k} (1 + j*x^j).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =2a(6) =3a(7) =1a(8) =2a(9) =5a(10) =4a(11) =7a(12) =8a(13) =5a(14) =7a(15) =11a(16) =15a(17) =22a(18) =17a(19) =31a(20) =39a(21) =20a(22) =31a(23) =39a(24) =64a(25) =81a(26) =85a(27) =125a(28) =97a(29) =170