[ exp(1/23)*n! ].

Terms

a(0) =1a(1) =2a(2) =6a(3) =25a(4) =125a(5) =751a(6) =5263a(7) =42111a(8) =379005a(9) =3790054a(10) =41690594a(11) =500287132a(12) =6503732722a(13) =91052258112