a(n) = 7*(10^(2n+1)-1)/9 - 2*10^n.A332175a(n) = 7*(10^(2n+1)-1)/9 - 2*10^n.Terms a(0) =5a(1) =757a(2) =77577a(3) =7775777a(4) =777757777a(5) =77777577777External referencesoeis: A332175