a(n) = e^2 * Sum_{k=0..n-1} Gamma(k + 1, 2).

Terms

a(0) =0a(1) =1a(2) =4a(3) =14a(4) =52a(5) =220a(6) =1092a(7) =6388a(8) =43588a(9) =341444a(10) =3022660a(11) =29835844a(12) =324782916a(13) =3864151876a(14) =49875956548a(15) =694041238340