a(n) = n - 1 + Sum_{j=0..n} j!.

Terms

a(0) =0a(1) =2a(2) =5a(3) =12a(4) =37a(5) =158a(6) =879a(7) =5920a(8) =46241a(9) =409122a(10) =4037923a(11) =43954724a(12) =522956325a(13) =6749977126a(14) =93928268327