20402760domain: NAppears in sequencesNumbers k such that 1*k + 1, 3*k + 1, 9*k + 1, 27*k + 1, 81*k + 1, 243*k + 1 are all primes.at n=20A112043Numbers k such that (3^j)*k + 1 are primes for j=0 to 6.at n=1A112129