[ exp(2/23)*n! ].

Terms

a(0) =1a(1) =2a(2) =6a(3) =26a(4) =130a(5) =785a(6) =5497a(7) =43983a(8) =395847a(9) =3958473a(10) =43543211a(11) =522518536a(12) =6792740972a(13) =95098373611