a(n) = Sum_{prime p <= n} n!/p!.

Terms

a(0) =1a(1) =4a(2) =16a(3) =81a(4) =486a(5) =3403a(6) =27224a(7) =245016a(8) =2450160a(9) =26951761a(10) =323421132a(11) =4204474717a(12) =58862646038a(13) =882939690570