[ exp(8/9)*n! ].

Terms

a(0) =2a(1) =4a(2) =14a(3) =58a(4) =291a(5) =1751a(6) =12259a(7) =98075a(8) =882678a(9) =8826785a(10) =97094640a(11) =1165135684a(12) =15146763898a(13) =212054694576