[ exp(6/13)*n! ].

Terms

a(0) =1a(1) =3a(2) =9a(3) =38a(4) =190a(5) =1142a(6) =7996a(7) =63968a(8) =575713a(9) =5757138a(10) =63328518a(11) =759942216a(12) =9879248812a(13) =138309483370