a(n) = (10^(2*n+1) - 1)/9 + 6*10^n.A332117a(n) = (10^(2*n+1) - 1)/9 + 6*10^n.Terms a(0) =7a(1) =171a(2) =11711a(3) =1117111a(4) =111171111a(5) =11111711111External referencesoeis: A332117