a(n) = 5*(10^(2*n+1)-1)/9 + 2*10^n.A332157a(n) = 5*(10^(2*n+1)-1)/9 + 2*10^n.Terms a(0) =7a(1) =575a(2) =55755a(3) =5557555a(4) =555575555a(5) =55555755555External referencesoeis: A332157