a(n) = 5*(10^(2*n+1)-1)/9 - 2*10^n.A332153a(n) = 5*(10^(2*n+1)-1)/9 - 2*10^n.Terms a(0) =3a(1) =535a(2) =55355a(3) =5553555a(4) =555535555a(5) =55555355555External referencesoeis: A332153