[ exp(1/4)*n! ].

Terms

a(0) =1a(1) =2a(2) =7a(3) =30a(4) =154a(5) =924a(6) =6471a(7) =51771a(8) =465947a(9) =4659471a(10) =51254185a(11) =615050229a(12) =7995652977a(13) =111939141684