One more than the partial sums of A219661.

Terms

a(0) =1a(1) =2a(2) =4a(3) =9a(4) =28a(5) =111a(6) =539a(7) =3150a(8) =21623a(9) =172349a(10) =1549897a(11) =15401145a(12) =168011253a(13) =2003304294a(14) =25928878273a(15) =361788001016