[ exp(2/5)*n! ].

Terms

a(0) =1a(1) =2a(2) =8a(3) =35a(4) =179a(5) =1074a(6) =7518a(7) =60150a(8) =541353a(9) =5413533a(10) =59548868a(11) =714586417a(12) =9289623422a(13) =130054727910