a(n) = 10^(2n+1) - 1 - 6*10^n.

A332193

a(n) = 10^(2n+1) - 1 - 6*10^n.

Terms

    a(0) =3a(1) =939a(2) =99399a(3) =9993999a(4) =999939999a(5) =99999399999

External references