21319

Properties

Appears in sequences

• Primes of the form k^2 + 3.at n=24A049423
• Primes with 14 as smallest positive primitive root.at n=14A061327
• Numbers k such that 71^k - 70^k is prime.at n=5A062637
• a(1) = 3; a(2n) = smallest prime starting (in the most significant digits) with a(2n-1) (i.e., as a right concatenation of a(2n-1) and a number with no insignificant zeros); a(2n+1) = smallest prime ending in (the least significant digits) a(2n-1). Alternate left and right concatenation yielding primes.at n=4A069615
• a(1) = 3; a(2n) = smallest prime starting (most significant digits) with a(2n-1). a(2n+1) = smallest prime ending (least significant digits)in a(2n).at n=4A069630
• Smallest prime p == 7 mod 8 (A007521) and p > prime(n+2) such that p is a quadratic residue mod the first n odd primes 3, 5, 7, 11, ..., prime(n+1), and p is a quadratic non-residue mod prime(n+2).at n=7A096640
• Numbers n such that 8*10^n + R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.at n=7A103071
• Let p = prime(sigma(n)) and q = prime(phi(n)), then p is in the sequence if p-q = 6.at n=27A103176
• Primes p equal to the sum of two successive sexy primes - 1 such that p - 6 is also prime.at n=30A104047
• a(n) = A007290(n+2) - 1 = 2*C(n+2,3) - 1.at n=39A108766
• Primes of the form 2x^3 + x + 1.at n=7A114350
• Duplicate of A049423.at n=24A121825
• 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=25A125765
• Smallest prime p such that the maximum run length of consecutive quadratic nonresidues modulo p is n.at n=20A129201
• 3n^3 + 2n^2 + n + 1.at n=19A130884
• a(n) = 15*n^2 - 9*n + 1.at n=38A134154
• Primes congruent to 30 mod 61.at n=38A142828
• Primes of the form p + (p^2 - 1)/8, where p is also prime.at n=20A165352
• Primes p dividing every A167859(m) from m=(p-1)/2 to m=(p-1).at n=28A167860
• Partial sums of A034897.at n=12A174226