a(n) = e^3 * Sum_{k=0..n-1} Gamma(k + 1, 3).

Terms

a(0) =0a(1) =1a(2) =5a(3) =22a(4) =100a(5) =493a(6) =2701a(7) =16678a(8) =116704a(9) =923473a(10) =8204077a(11) =81069166a(12) =882762292a(13) =10503611245a(14) =135576241957