670033

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=13A033181
• Kaprekar numbers: numbers k such that k = q + r and k^2 = q*10^m + r, for some m >= 1, q >= 0 and 0 <= r < 10^m. Here q and r must both have the same number of digits.at n=25A045913
• The full list of 6-Kaprekar numbers.at n=22A053397
• Carmichael numbers with exactly 4 prime factors.at n=14A074379
• Pseudoprimes to bases 2, 3 and 5.at n=29A083737
• Carmichael numbers with more than 3 prime factors.at n=14A141711
• Composite numbers n with the property that phi(n) divides (n-1)^2.at n=34A173703
• Carmichael numbers of the form C = p*(2p-1)*(n*(2p-2)+p), where p and 2p-1 are prime numbers.at n=12A182207
• Carmichael numbers divisible by 7.at n=12A182208
• a(n) = (15^n - (-2)^n)/17.at n=6A239285
• 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=1A277366
• Numbers n > 2 such that A258409(n)*A002322(n) divides n-1.at n=6A284671
• Square roots of terms in A238237.at n=29A290449
• Carmichael numbers k such that phi(k) divides (k-1)*lambda(k).at n=14A306338
• Carmichael numbers m such that A309132(m) < m.at n=5A309268
• Carmichael numbers k for which A053575(k) [the odd part of phi] does not divide k-1.at n=26A340092
• Carmichael numbers ending in 3.at n=3A355309
• The greater of twin Carmichael numbers: a pair of consecutive Carmichael numbers (A002997) without a non-prime-power weak Carmichael number (A087442) between them.at n=4A365023
• Odd numbers k > 1 such that gcd(5,k) = 1 and 5^((k-1)/2) == -(5/k) (mod k), where (5/k) is the Jacobi symbol (or Kronecker symbol); Euler pseudoprimes to base 5 (A262052) that are not Euler-Jacobi pseudoprimes to base 5 (A375914).at n=27A375816