[ exp(6/7)*n! ].

Terms

a(0) =2a(1) =4a(2) =14a(3) =56a(4) =282a(5) =1696a(6) =11876a(7) =95010a(8) =855097a(9) =8550971a(10) =94060683a(11) =1128728204a(12) =14673466654a(13) =205428533159