A241487 Primes p such that p+6, p+666 and p+6666 are also prime.

7, 53, 67, 157, 191, 311, 331, 347, 353, 373, 443, 563, 571, 641, 821, 823, 857, 941, 1033, 1087, 1123, 1283, 1423, 1607, 1621, 1873, 1997, 2011, 2137, 2333, 2383, 2543, 2657, 2677, 2797, 2957, 3301, 3511, 3607, 3671, 3691, 3797, 3847, 4133, 5113, 5147, 5231

Offset: 1

Author

K. D. Bajpai, Apr 23 2014

Keywords

• nonn

Comments

The constants in the definition (6, 666 and 6666) are concatenations of the digit 6.

Examples

			a(2) = 53 is a prime: 53+6 = 59, 53+666 = 719 and 53+6666 = 6719 are also prime.
a(3) = 67 is a prime: 67+6 = 73, 67+666 = 733 and 67+6666 = 6733 are also prime.
		

Links

• K. D. Bajpai, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000040, A023200, A046136, A230223, A236302, A236304, A237890, A241485.

Programs

Maple

KD:= proc() local a,b,d,e; a:= ithprime(n); b:=a+2;d:=a+222;e:=a+2222; if isprime(b)and isprime(d)and isprime(e)  then return (a) :fi; end: seq(KD(), n=1..5000);

Mathematica

KD = {}; Do[p = Prime[n];If[PrimeQ[p + 6] && PrimeQ[p + 666] && PrimeQ[p + 6666],AppendTo[KD, p]], {n, 5000}]; KD
(*For the b-file*) c = 0; p = Prime[n]; Do[If[PrimeQ[p + 6] && PrimeQ[p + 666] && PrimeQ[p + 6666], c = c + 1;Print[c, "  ", p]], {n, 1, 2*10^6}];

PARI

s=[]; forprime(p=2, 6000, if(isprime(p+6) && isprime(p+666) && isprime(p+6666), s=concat(s, p))); s \\ Colin Barker, Apr 25 2014