a(n) = 2^(n-7)*(n^4 - 6*n^3 + 59*n^2 - 54*n)/3.

Terms

a(0) =0a(1) =0a(2) =1a(3) =6a(4) =25a(5) =90a(6) =300a(7) =952a(8) =2912a(9) =8640a(10) =24960a(11) =70400a(12) =194304a(13) =525824a(14) =1397760a(15) =3655680a(16) =9420800a(17) =23953408a(18) =60162048a(19) =149422080a(20) =367329280a(21) =894566400a(22) =2159804416a(23) =5173149696a(24) =12299796480a(25) =29045555200a(26) =68157440000a(27) =158997676032a(28) =368880648192a(29) =851443712000