a(n) = n! * Sum_{k=1..n} 1/(k*floor(n/k)).

Terms

a(0) =1a(1) =2a(2) =7a(3) =26a(4) =148a(5) =804a(6) =6228a(7) =47424a(8) =441936a(9) =4288320a(10) =50437440a(11) =560373120a(12) =7723935360a(13) =106618256640