[ exp(7/18)*n! ].

Terms

a(0) =1a(1) =2a(2) =8a(3) =35a(4) =177a(5) =1062a(6) =7435a(7) =59485a(8) =535371a(9) =5353716a(10) =58890876a(11) =706690515a(12) =9186976699a(13) =128617673796