489997

Appears in sequences

• Semiprime 2-pseudoprimes of the form 10k + 7.at n=16A216667
• Composite numbers k congruent to 5 (mod 8) such that 2^((k-1)/2) mod k = k-1.at n=9A244626
• 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=13A307767
• Pseudoprimes congruent to 7 mod 10.at n=19A317972
• Odd composite numbers k such that 2^((k-1)/2) == -1 (mod k).at n=10A356638