a(n) = floor(exp(2/17)*n!).

Terms

a(0) =1a(1) =2a(2) =6a(3) =26a(4) =134a(5) =809a(6) =5669a(7) =45353a(8) =408184a(9) =4081844a(10) =44900294a(11) =538803530a(12) =7004445892a(13) =98062242500