[ exp(1/22)*n! ].

Terms

a(0) =1a(1) =2a(2) =6a(3) =25a(4) =125a(5) =753a(6) =5274a(7) =42195a(8) =379755a(9) =3797551a(10) =41773068a(11) =501276819a(12) =6516598658a(13) =91232381215