a(n) = n! * Sum_{d|n} mu(n/d) / d!.

Terms

a(0) =1a(1) =-1a(2) =-5a(3) =-11a(4) =-119a(5) =241a(6) =-5039a(7) =-1679a(8) =-60479a(9) =1784161a(10) =-39916799a(11) =218877121a(12) =-6227020799a(13) =43571848321a(15) =-518918399