a(n) = 2*(10^(2n+1)-1)/9 + 7*10^n.A332129a(n) = 2*(10^(2n+1)-1)/9 + 7*10^n.Terms a(0) =9a(1) =292a(2) =22922a(3) =2229222a(4) =222292222a(5) =22222922222External referencesoeis: A332129