Base 10 digital convolution sequence.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =24a(5) =120a(6) =720a(7) =5040a(8) =40320a(9) =362880a(10) =40320a(11) =403200a(12) =846720a(13) =2943360a(14) =12620160a(15) =66044160a(16) =408885120a(17) =2928240000a(18) =23834805120a(19) =217441486080a(20) =47669610240a(21) =482552582400