[ exp(4/13)*n! ].

Terms

a(0) =1a(1) =2a(2) =8a(3) =32a(4) =163a(5) =979a(6) =6855a(7) =54846a(8) =493619a(9) =4936192a(10) =54298119a(11) =651577434a(12) =8470506649a(13) =118587093099