a(n) = Sum_{d divides n} (d!)^(n/d).

Terms

a(0) =1a(1) =3a(2) =7a(3) =29a(4) =121a(5) =765a(6) =5041a(7) =40913a(8) =363097a(9) =3643233a(10) =39916801a(11) =479535185a(12) =6227020801a(13) =87203692929