[ exp(8/13)*n! ].

Terms

a(0) =1a(1) =3a(2) =11a(3) =44a(4) =222a(5) =1332a(6) =9325a(7) =74606a(8) =671461a(9) =6714615a(10) =73860775a(11) =886329300a(12) =11522280912a(13) =161311932777