Partial sums of A038034.

Terms

a(0) =1a(1) =3a(2) =6a(3) =13a(4) =21a(5) =73a(6) =126a(7) =414a(8) =1623a(9) =6870a(10) =12118a(11) =83513a(12) =154909a(13) =530688a(14) =7488221a(15) =59799083a(16) =112109946a(17) =1264732499a(18) =2417355053a(19) =47993257518