[ exp(13/17)*n! ].

Terms

a(0) =2a(1) =4a(2) =12a(3) =51a(4) =257a(5) =1546a(6) =10827a(7) =86621a(8) =779597a(9) =7795977a(10) =85755752a(11) =1029069031a(12) =13377897415a(13) =187290563819