a(n) = ceiling((n/e)^n).

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =5a(5) =22a(6) =116a(7) =751a(8) =5629a(9) =47812a(10) =454000a(11) =4765191a(12) =54782415a(13) =684597511a(14) =9239952803a(15) =133952757202