a(n) = 27*((10^n - 1)/9)^2.A178631a(n) = 27*((10^n - 1)/9)^2.Terms a(0) =27a(1) =3267a(2) =332667a(3) =33326667a(4) =3333266667a(5) =333332666667External referencesoeis: A178631