a(n) = ceiling(((10^n - 1)^2/9 + 10^n)/18).

A202606

a(n) = ceiling(((10^n - 1)^2/9 + 10^n)/18).

Terms

    a(0) =1a(1) =2a(2) =67a(3) =6217a(4) =617717a(5) =61732717a(6) =6172882717a(7) =617284382717

External references