a(n) = (10^(2*n+1) - 1)/9 + 7*10^n.A332118a(n) = (10^(2*n+1) - 1)/9 + 7*10^n.Terms a(0) =8a(1) =181a(2) =11811a(3) =1118111a(4) =111181111a(5) =11111811111External referencesoeis: A332118