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

Terms

a(0) =1a(1) =3a(2) =14a(3) =66a(4) =444a(5) =2880a(6) =25080a(7) =216720a(8) =2247840a(9) =24071040a(10) =304335360a(11) =3752179200a(12) =54965433600a(13) =810550540800