[ exp(4/19)*n! ].

Terms

a(0) =1a(1) =2a(2) =7a(3) =29a(4) =148a(5) =888a(6) =6221a(7) =49768a(8) =447912a(9) =4479127a(10) =49270405a(11) =591244864a(12) =7686183235a(13) =107606565290