397792domain: NAppears in sequencesNumbers n such that 10000000n+1, 10000000n+3, 10000000n+7, 10000000n+9 are all primes.at n=23A064966a(n) is the number of covering relations in the poset P of n X n idempotent matrices over GF(2) ordered by A <= B if and only if AB = BA = A.at n=5A357410