a(n) = 2*(10^(2n+1)-1)/9 + 2*10^n.A332124a(n) = 2*(10^(2n+1)-1)/9 + 2*10^n.Terms a(0) =4a(1) =242a(2) =22422a(3) =2224222a(4) =222242222a(5) =22222422222External referencesoeis: A332124