a(n) = n * Sum_{d|n} (d + n/d - 2)!/d!.

Terms

a(0) =1a(1) =3a(2) =7a(3) =29a(4) =121a(5) =745a(6) =5041a(7) =40425a(8) =362917a(9) =3629411a(10) =39916801a(11) =479006233a(12) =6227020801a(13) =87178326495