A247590 Primes p such that p + 6^k is also prime at least for k = 1, 2, 3 and 4.

7, 11, 23, 131, 157, 193, 227, 271, 331, 571, 947, 977, 1013, 1087, 1283, 1453, 1657, 1871, 2341, 2671, 2693, 3607, 3637, 3691, 4013, 4951, 5407, 5653, 6211, 6353, 6653, 6827, 6977, 6991, 7541, 7717, 8053, 8081, 8537, 9203, 9613, 9643, 10853, 11113, 11251, 11933

Offset: 1

Author

K. D. Bajpai, Sep 20 2014

Keywords

• nonn
• easy

Examples

			a(1) = 7 is prime. 7 + 6^1 = 13, 7 + 6^2 = 43, 7 + 6^3 = 223 and 7 + 6^4 = 1303 are also prime. It is the smallest such set of 5 primes; (Quintet).
		

Links

• K. D. Bajpai, Table of n, a(n) for n = 1..12638

Crossrefs

Cf. A000040, A049494, A049495.

Programs

Mathematica

Select[k = {1, 2, 3, 4}; Prime[Range[500]], And @@ PrimeQ[# + 6^k] &]

PARI

forprime(p=1,10^4,c=1;for(k=1,4,if(!isprime(p+6^k),c--;break));if(c,print1(p,", "))) \\ Derek Orr, Sep 20 2014