[ exp(3/13)*n! ].

Terms

a(0) =1a(1) =2a(2) =7a(3) =30a(4) =151a(5) =906a(6) =6348a(7) =50785a(8) =457072a(9) =4570722a(10) =50277945a(11) =603335344a(12) =7843359474a(13) =109807032639