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

Terms

a(0) =1a(1) =2a(2) =3a(3) =6a(4) =8a(5) =15a(6) =21a(7) =34a(8) =47a(9) =74a(10) =99a(11) =151a(12) =201a(13) =287a(14) =383a(15) =540a(16) =701a(17) =970a(18) =1255a(19) =1688a(20) =2171a(21) =2882a(22) =3657a(23) =4801a(24) =6058a(25) =7819a(26) =9816a(27) =12566a(28) =15619a(29) =19826