1909001

Appears in sequences

• Carmichael numbers which are also base-2 strong pseudoprimes.at n=5A063847
• Pseudoprimes to bases 2, 3, 5 and 7.at n=26A083739
• 3-Carmichael numbers: Carmichael numbers equal to the product of 3 primes: k = p*q*r, where p < q < r are primes such that a^(k-1) == 1 (mod k) if a is prime to k.at n=29A087788
• Carmichael numbers C such that C-1 is not a Niven/Harshad number.at n=11A097061
• Carmichael numbers that are not == 1 mod 24.at n=17A097130
• Carmichael numbers that are not == 1 mod 12. There are 69 Carmichael numbers out to 2*m+1, m=2*10^6 and all but the above 9 are 1 mod 12.at n=8A110889
• Strong pseudoprimes (base-2) equal to product of 3 primes not necessarily distinct.at n=11A112450
• Icosagonal numbers for which the sum of the digits is also an icosagonal number.at n=23A117799
• Sarrus numbers that become prime when two is added.at n=29A137198
• Numbers k such that at least one of k and k+2 is composite, while for every b coprime to k*(k+2), b^(k-1) == 1 (mod k) and b^(k+1) == 1 (mod k+2).at n=18A194231
• Carmichael numbers not congruent to 1 modulo 6.at n=5A205947
• Intersection of A001567 and A212502.at n=29A212601
• Carmichael numbers that have only prime divisors of the form 10k+1.at n=6A212843
• Composite numbers k such that k divides Fibonacci(k+1) or Fibonacci(k-1) and 2^(k-1) == 1 (mod k).at n=23A214434
• Pseudoprimes to a twin prime criterion of Aebi and Cairns.at n=30A224695
• Strong pseudoprimes (base 2) that become prime when two is added.at n=5A230484
• Strong pseudoprimes k to base 2 such that either k-2 or k+2 is prime.at n=19A230487
• Carmichael numbers (A002997) that are not absolute Euler pseudoprimes (A033181).at n=34A262043
• Carmichael numbers (A002997) that are the sum of two squares.at n=16A265237
• Irregular triangle read by rows in which row n contains the first Carmichael number equal to m mod n where m is coprime to n, 0 <= m < n, ordered by m.at n=23A278338