a(n) = (n! - 5)/5.

Terms

a(0) =23a(1) =143a(2) =1007a(3) =8063a(4) =72575a(5) =725759a(6) =7983359a(7) =95800319a(8) =1245404159a(9) =17435658239a(10) =261534873599