a(n) = denominator(Sum_{k=1..n} k^2/k!).

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =6a(5) =8a(6) =40a(7) =720a(8) =1680a(9) =13440a(10) =362880a(11) =1209600a(12) =4435200a(13) =68428800a(14) =296524800a(15) =29059430400