[ exp(5/18)*n! ].

Terms

a(0) =1a(1) =2a(2) =7a(3) =31a(4) =158a(5) =950a(6) =6653a(7) =53230a(8) =479071a(9) =4790715a(10) =52697871a(11) =632374457a(12) =8220867953a(13) =115092151350