a(n) = 7*(10^(2*n+1) - 1)/9 + 10^n.A332178a(n) = 7*(10^(2*n+1) - 1)/9 + 10^n.Terms a(0) =8a(1) =787a(2) =77877a(3) =7778777a(4) =777787777a(5) =77777877777External referencesoeis: A332178