21839

Properties

Appears in sequences

• Denominators of continued fraction convergents to sqrt(619).at n=11A042189
• Smaller of twin primes whose middle term is a multiple of A002110(4)=210.at n=18A060230
• Primes p such that the number of distinct prime divisors of all composite numbers between p and the next prime is 5.at n=34A075585
• Primes p such that 13 is the largest of all prime factors of the numbers between p and the next prime (cf. A052248).at n=22A080188
• a(n) is the smallest x such that the quotient d(x+1)/d(x) equals n, where d = A000005.at n=39A080371
• Primes of the form 2*n^2 + 2*n - 1.at n=33A098828
• Highly cototient numbers that are prime, or intersection of A000040 and A100827.at n=37A105440
• Primes p such that p + 2 and p*(p + 2) + 2 are primes.at n=39A108013
• Consider the array T(n, m) = m-th prime of the form n*i(i+1)/2 +/- 1. This sequence is the main diagonal.at n=27A125765
• a(n) is n-th prime == -1 (mod 6n).at n=39A138905
• Lesser p of twin primes (p,q) such that there exists an integer between sqrt(2p) and sqrt(2q).at n=19A145701
• Twin prime pairs p, p+2 such that p+(p+2)+1 and p*(p+2)+1 are both square.at n=20A166564
• Primes p dividing every A167859(m) from m=(p-1)/2 to m=(p-1).at n=29A167860
• Primes p such that 3*p+2, 5*p+4 and 7*p+6 are also prime.at n=22A173876
• List of primes p1 such that (p1,p2) are twin primes where both 2*p1+p2 and p1+2*p2 are primes.at n=12A174920
• Lesser of twin primes p1 such that p1+(p2^2-p1^2) and p2+(p2^2-p1^2) are prime numbers.at n=29A174922
• Primes of the form highly abundant number - 1.at n=52A181562
• Least number k>1 such that (tau(k-1)+tau(k+1))/tau(k) = n where tau = A000005.at n=43A190644
• (Partial sums of the squarefree integers) that are prime.at n=12A194128
• Primes congruent to 1 mod 61.at n=39A212378