449065

Appears in sequences

• Carmichael numbers: composite numbers k such that a^(k-1) == 1 (mod k) for every a coprime to k.at n=30A002997
• Absolute Euler pseudoprimes: odd composite numbers n such that a^((n-1)/2) == +-1 (mod n) for every a coprime to n.at n=9A033181
• Carmichael numbers with exactly 4 prime factors.at n=10A074379
• Pseudoprimes to bases 2 and 7.at n=24A083733
• Pseudoprimes to bases 2,3 and 7.at n=19A083738
• Pseudoprimes (base-2) equal to product of 4 primes not necessarily distinct.at n=26A112441
• Nonprime numbers k such that k divides 3^((k+1)/2) - 2^((k+1)/2) - 1.at n=31A130062
• Carmichael numbers with more than 3 prime factors.at n=10A141711
• Composite numbers n with the property that phi(n) divides (n-1)^2.at n=29A173703
• Fermat pseudoprimes to base 2 divisible by 5.at n=23A216023
• Numbers n > 2 such that A258409(n)*A002322(n) divides n-1.at n=4A284671
• Composite numbers k such that p^(k-1) == 1 (mod k) for every prime p strongly prime to k.at n=32A323214
• Carmichael numbers k for which A053575(k) [the odd part of phi] divides k-1.at n=10A339869
• Intersection of A137409 and A339870: Composite numbers k of the form 4u+1 having more than one prime factor of type 4u+3, and for which the odd part of phi(k) divides k-1.at n=12A339875
• Carmichael numbers ending in 5.at n=5A355305
• a(n) is the smallest n-gonal number that is a Fermat pseudoprime to base 2 (A001567), or -1 if no such number exists.at n=24A371759