a(n) = [x^n] 1/(1-x)^n * Product_{k=1..n} 1/(1-x^k).

Terms

a(0) =1a(1) =2a(2) =7a(3) =25a(4) =92a(5) =343a(6) =1292a(7) =4902a(8) =18703a(9) =71677a(10) =275694a(11) =1063636a(12) =4114131a(13) =15948762a(14) =61946290a(15) =241013869a(16) =939125870a(17) =3664299332a(18) =14314777054a(19) =55982787136a(20) =219158088711a(21) =858728875776