21601

Properties

Appears in sequences

• Half-quartan primes: primes of the form p = (x^4 + y^4)/2.at n=12A002646
• Primes of the form k^2 - 8.at n=34A028886
• Primes that are palindromic in base 12.at n=28A029979
• Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 88 ones.at n=26A031856
• phi(n) is equal to the product of the dual prime-power components of n-1 (i.e., A008477(n-1)).at n=7A039783
• Prime number spiral (clockwise, North spoke).at n=25A054551
• Number of distinct differences between consecutive divisors (ordered by increasing magnitude) of n! which are not also divisors of n!.at n=22A060738
• Primes p such that the greatest prime divisor of p-1 is 5.at n=39A061599
• a(n) = 2*prime(n)^2 - prime(n+1)^2.at n=34A064051
• Primes which can be expressed as concatenation of powers of 6 and 0's.at n=23A066597
• Primes p such that x^5 = 2 has a solution mod p, but x^(5^2) = 2 has no solution mod p.at n=16A070182
• Primes p such that the period of the decimal expansion of 1/p is a square.at n=29A072858
• Numbers k such that k, sigma(k) and phi(k) have the same decimal digits (ignoring multiplicity).at n=34A082059
• Primes arising in A084728.at n=5A084729
• A000041(n)-A000010(n).at n=36A086739
• Smallest prime p that is a palindrome in n different bases < p.at n=9A087911
• Primes of the form 6*k^2 + 1.at n=18A090687
• Primes of the form 2^a * 3^b * 5^c + 1 for positive a, b, c.at n=30A114991
• The smallest prime of the form (prime(n+1)^k + prime(n+2)^k)/2 for positive integer k.at n=3A121710
• a(n) = smallest odd m such that (m^n + (m+2)^n)/2 is prime.at n=5A121923