1678541

Appears in sequences

• Brilliant Sarrus numbers.at n=24A086837
• Sarrus numbers that become prime when two is added.at n=26A137198
• Lesser of overpseudo-twin-primes to base 2 defined in Comment.at n=9A195468
• Pseudoprimes to a twin prime criterion of Aebi and Cairns.at n=27A224695
• Strong pseudoprimes (base 2) that become prime when two is added.at n=4A230484
• Strong pseudoprimes k to base 2 such that either k-2 or k+2 is prime.at n=17A230487
• Composite numbers k congruent to 5 (mod 8) such that 2^((k-1)/2) mod k = k-1.at n=17A244626
• Numbers k > 1 such that 2^k == 2 (mod k) and gcd(k, 3^k - 3) = 1.at n=22A300762
• The "non-residue" pseudoprimes: odd composite numbers n such that b(n)^((n-1)/2) == -1 (mod n), where base b(n) = A020649(n).at n=33A307767
• Numbers k such that 2^(k-1) == 1 (mod k) and p-1 does not divide k-1 for every prime p dividing k.at n=31A316907
• Odd composite numbers k such that 2^((k-1)/2) == -1 (mod k).at n=25A356638