1509709

Appears in sequences

• Composite numbers k congruent to 5 (mod 8) such that 2^((k-1)/2) mod k = k-1.at n=16A244626
• 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=30A307767
• Odd composite numbers k such that 2^((k-1)/2) == -1 (mod k).at n=23A356638