a(n) = 9*8*7*6*5*4*3*2*1 + 18*17*16*15*14*13*12*11*10 + ... + (up to the n-th term).

Terms

a(0) =9a(1) =72a(2) =504a(3) =3024a(4) =15120a(5) =60480a(6) =181440a(7) =362880a(8) =362880a(9) =362898a(10) =363186a(11) =367776a(12) =436320a(13) =1391040a(14) =13728960a(15) =160755840a(16) =1764685440a(17) =17643588480a(18) =17643588507a(19) =17643589182a(20) =17643606030a(21) =17644009680a(22) =17653276080a(23) =17856715680a(24) =22119259680a(25) =107157012480