6290339domain: NAppears in sequencesPositive integers k such that k divides 12^k - 1.at n=28A014951Numbers n dividing u(n), where the Lucas sequence is defined u(i) = u(i-1) - 3*u(i-2) with initial conditions u(0)=0, u(1)=1.at n=32A228440Numbers k such that sigma_2(k) = sigma_2(phi(k)).at n=7A333338