From the powers that be.

Terms

a(0) =0a(1) =1a(2) =2a(3) =5a(4) =10a(5) =40a(6) =40a(7) =105a(8) =5627a(9) =14501a(10) =330861a(11) =658110a(12) =897229a(13) =26673531a(14) =180566007a(15) =180566007a(16) =19299107624