G.f.: Sum_{k>=0} x^(k*(k+1)/2) * Product_{j=1..k} 1/(1 - x^j)^3.

Terms

a(0) =1a(1) =1a(2) =3a(3) =7a(4) =13a(5) =24a(6) =41a(7) =70a(8) =114a(9) =186a(10) =293a(11) =459a(12) =703a(13) =1067a(14) =1593a(15) =2359a(16) =3447a(17) =4998a(18) =7175a(19) =10222a(20) =14445a(21) =20277a(22) =28263a(23) =39156a(24) =53922a(25) =73843a(26) =100587a(27) =136331a(28) =183890a(29) =246909