a(n) = 6*(10^(2*n+1)-1)/9 - 2*10^n.A332164a(n) = 6*(10^(2*n+1)-1)/9 - 2*10^n.Terms a(0) =4a(1) =646a(2) =66466a(3) =6664666a(4) =666646666a(5) =66666466666External referencesoeis: A332164