Partial sums of A219661.

Terms

a(0) =0a(1) =1a(2) =3a(3) =8a(4) =27a(5) =110a(6) =538a(7) =3149a(8) =21622a(9) =172348a(10) =1549896a(11) =15401144a(12) =168011252a(13) =2003304293a(14) =25928878272a(15) =361788001015