a(n) = Sum_{k=1..n} mu(k) * k^(n - k).

Terms

a(0) =1a(1) =0a(2) =-2a(3) =-6a(4) =-17a(5) =-46a(6) =-132a(7) =-402a(8) =-1314a(9) =-4613a(10) =-17313a(11) =-68893a(12) =-288556a(13) =-1269637a(14) =-5907157a(15) =-29489299a(16) =-160431708a(17) =-955478664a(18) =-6145884133a(19) =-41584238971a(20) =-287650358748