21911

Properties

Appears in sequences

• From table of maximal epacts e(p) and corresponding primes p, for x_1=2, x_{m+1} = (x_m)^2+1; sequence gives p.at n=33A014424
• Primes p such that p+1 is palindromic.at n=32A028981
• Least prime in A031936 (lesser of 18-twins) whose distance to the next 18-twin is 2*n.at n=7A052358
• Balanced primes separated from the next lower and next higher prime neighbors by 18.at n=1A053073
• Sixth term of weak prime sextet: p(m-4)-p(m-5) < p(m-3)-p(m-4) < p(m-2)-p(m-3) < p(m-1)-p(m-2) < p(m)-p(m-1).at n=8A054833
• Numbers k such that (12^k + 1)/13 is a prime.at n=7A057178
• Numerators of the determinant of matrix (M(n) - H(n)), where H(n) is the n-th Hilbert matrix and M(n) is an n X n matrix with i,j-th entry i+j-1.at n=9A061913
• a(n) is smallest prime > 2*a(n-1), a(1) = 3.at n=12A065545
• Primes of the form k^2 + 7.at n=40A079138
• Primes p such that the next prime after p can be obtained from p by adding the product of the digits of p.at n=13A089823
• a(1) = 1; a(n) = nextprime(2*a(n-1)) for n > 1.at n=13A110930
• Two-sided multiplicative pointer primes.at n=1A125840
• Primes which are the sum of the first k nonprimes for some k >= 2.at n=20A128927
• Prime numbers, isolated from neighboring primes by >16.at n=24A137875
• Primes congruent to 22 mod 59.at n=39A142749
• Primes of the form (4k^2 + 4k - 5)/5.at n=20A154619
• Values of A167053(k)-A167053(k-1)-1 not equal to 1.at n=11A167054
• Primes p such that f(f(p)) is prime, where f(x) = x^4 + x^3 + x^2 + x + 1 = A053699(x).at n=22A237445
• Primes p such that f(f(p)) is prime where f(x) = Phi_6(x).at n=12A237446
• a(1) = 0; and for n > 1, a(n) = 2*a(A285712(n)) + [0 == (n mod 3)].at n=29A292590