1809697

Appears in sequences

• Poulet numbers of the form (6k+1)*(24k+1).at n=9A182123
• 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=34A307767
• Fermat pseudoprimes to base 2 that are decagonal.at n=28A321870
• Chebyshev pseudoprimes to both base 2 and base 3: composite numbers k such that T(k, 2) == 2 (mod k) and T(k, 3) == 3 (mod k), where T(k, x) is the k-th Chebyshev polynomial of the first kind.at n=33A330208
• Composite numbers k == 3, 7 (mod 10) such that 5^((k-1)/2) == -1 (mod k).at n=15A375916