a(n) = phi(10^n-1)/n, where phi is Euler's totient function (A000010).

A295497

a(n) = phi(10^n-1)/n, where phi is Euler's totient function (A000010).

Terms

    a(0) =6a(1) =30a(2) =216a(3) =1500a(4) =12960a(5) =77760a(6) =948192a(7) =7344000a(8) =72071856a(9) =589032000a(10) =6060314304a(11) =38491200000a(12) =496775732544

External references