6840001

Appears in sequences

• Carmichael numbers divisible by 7.at n=23A182208
• Carmichael numbers divisible by 7 and 17.at n=1A182532
• Composite numbers k such that phi(k) divides 4*(k-1).at n=13A193167
• Number of (n+1)X(3+1) 0..1 arrays with the sum of each 2X2 subblock two median terms lexicographically nondecreasing columnwise and nonincreasing rowwise.at n=6A235760
• Number of (n+1)X(7+1) 0..1 arrays with the sum of each 2X2 subblock two median terms lexicographically nondecreasing columnwise and nonincreasing rowwise.at n=2A235764
• Composite numbers k such that phi(k)*lambda(k) divides (k-1)^2, where phi(k) = A000010(k) and lambda(k) = A002322(k).at n=2A277366
• Numbers n > 2 such that A258409(n)*A002322(n) divides n-1.at n=12A284671
• Carmichael numbers k such that phi(k) divides (k-1)*lambda(k).at n=20A306338
• The phi-radical numbers: composite numbers m such that rad(phi(m)) = rad(m-1).at n=33A306478
• Numbers that are both Fermat pseudoprimes to base 2 (A001567) and Bruckman-Lucas pseudoprimes (A005845).at n=30A329240
• Carmichael numbers k for which A053575(k) [the odd part of phi] divides k-1.at n=14A339869
• 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=27A339875
• 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=23A345753
• Carmichael numbers k such that k-1 is a Novak-Carmichael number.at n=16A375322