[ exp(18/19)*n! ].

Terms

a(0) =2a(1) =5a(2) =15a(3) =61a(4) =309a(5) =1856a(6) =12997a(7) =103981a(8) =935836a(9) =9358363a(10) =102941998a(11) =1235303982a(12) =16058951777a(13) =224825324882