a(n) = phi(n^n - 1)/n where phi is A000010.

A319183

a(n) = phi(n^n - 1)/n where phi is A000010.

Terms

    a(0) =1a(1) =4a(2) =32a(3) =280a(4) =5040a(5) =37856a(6) =829440a(7) =15676416a(8) =589032000a(9) =10374307328a(10) =388566097920

External references