[ exp(3/8)*n! ].

Terms

a(0) =1a(1) =2a(2) =8a(3) =34a(4) =174a(5) =1047a(6) =7333a(7) =58665a(8) =527987a(9) =5279872a(10) =58078601a(11) =696943215a(12) =9060261802a(13) =126843665237