A246901 a(n) is the n-th smallest prime p such that p+4n is also prime.

3, 5, 11, 31, 41, 23, 73, 131, 47, 97, 149, 83, 229, 167, 89, 337, 311, 167, 307, 293, 149, 499, 509, 211, 457, 509, 311, 607, 743, 211, 787, 839, 331, 877, 521, 419, 1171, 911, 421, 787, 1289, 419, 1279, 1103, 433, 1327, 1361, 619, 1123, 1103, 617, 1663, 1721, 661, 1039, 1553, 739, 2179, 2111, 599

Offset: 1

Author

Zak Seidov, Nov 16 2014

Keywords

• nonn

Comments

There is an array defined by: A(n,k) is the k-th smallest prime such that p+4*n is also prime (analog of A231608). It starts

3 7 13 19 37 43 67 79 97 103

3 5 11 23 29 53 59 71 89 101

5 7 11 17 19 29 31 41 47 59

3 7 13 31 37 43 67 73 97 151

3 11 17 23 41 47 53 59 83 89

5 7 13 17 19 23 29 37 43 47

3 13 19 31 43 61 73 79 103 109

5 11 29 41 47 71 107 131 149 167

5 7 11 17 23 31 37 43 47 53

3 7 13 19 31 43 61 67 73 97

a(n) = A(n,n) reads along the main diagonal of this array. - R. J. Mathar, Nov 19 2014

Links

• Zak Seidov, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A086505.

Programs

PARI

a(n) = nb=0; forprime(p=3,, if (isprime(p+4*n), nb++; if (nb==n, return (p)))); \\ Michel Marcus, Nov 16 2014