2704801

Appears in sequences

• Absolute Euler pseudoprimes: odd composite numbers n such that a^((n-1)/2) == +-1 (mod n) for every a coprime to n.at n=23A033181
• Carmichael numbers divisible by 11.at n=8A182090
• Composite numbers k such that k divides Fibonacci(k+1) or Fibonacci(k-1) and 2^(k-1) == 1 (mod k).at n=28A214434
• Carmichael numbers that are the average of two consecutive primes.at n=4A265669
• Sarrus numbers (A001567) that are the average of two consecutive primes.at n=21A265684
• Numbers n > 2 such that A258409(n)*A002322(n) divides n-1.at n=9A284671
• Carmichael numbers k such that phi(k) divides (k-1)*lambda(k).at n=16A306338
• The phi-radical numbers: composite numbers m such that rad(phi(m)) = rad(m-1).at n=29A306478
• Numbers that are both Fermat pseudoprimes to base 2 (A001567) and Bruckman-Lucas pseudoprimes (A005845).at n=20A329240
• Composite numbers k such that phi(k) divides d*(k - 1) for some squarefree divisor d of k - 1.at n=4A337316
• Euler-Fibonacci pseudoprimes: odd composites k such that F(k) == 5^((k-1)/2) == +-1 (mod k), where F(k) = A000045(k), the Fibonacci numbers.at n=14A345753
• Carmichael numbers ending in 1.at n=37A354609