[ exp(1/9)*n! ].

Terms

a(0) =1a(1) =2a(2) =6a(3) =26a(4) =134a(5) =804a(6) =5632a(7) =45058a(8) =405525a(9) =4055253a(10) =44607785a(11) =535293421a(12) =6958814485a(13) =97423402796