1507963

Appears in sequences

• Smith numbers which are also base-2 pseudoprimes.at n=8A063844
• Sarrus numbers k such that k-1 and k+1 have the same number of prime divisors (counted with multiplicity).at n=16A086806
• Composite numbers n such that n == 3 (mod 8) and 2^((n-1)/2) == -1 (mod n).at n=6A244628
• Fermat pseudoprimes (A001567) that are the sum of three consecutive primes.at n=13A270639
• Composite numbers k == 3 (mod 4) such that (1 + i)^k == 1 - i (mod k), where i = sqrt(-1).at n=14A270697
• Numbers k > 1 such that 2^k == 2 (mod k) and gcd(k, 3^k - 3) = 1.at n=20A300762
• Half thrice the previous number, rounded down, plus 1, starting with 6.at n=30A302748
• 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=29A307767
• Numbers k such that 2^(k-1) == 1 (mod k) and lpf(k)-1 does not divide k-1.at n=32A316906
• 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=29A316907
• Odd composite numbers k such that 2^((k-1)/2) == -1 (mod k).at n=22A356638