A235871 - OEIS

%I #13 Apr 23 2014 16:07:28

%S 5,17,107,617,857,1277,1487,2087,3167,3557,4217,6947,7457,7877,10067,

%T 12917,13217,14387,15137,17657,20897,21317,22367,22697,27407,27527,

%U 27917,28547,29207,29387,30467,31727,32117,33287,33617,35507,36107,47657,49367,49787

%N Primes p such that p+2, p+24 and p+246 are also primes.

%C All the terms in the sequence are congruent to 5 mod 6.

%C The constants in the definition (2, 24 and 246) are the concatenation of first even digits 2,4 and 6.

%H K. D. Bajpai, <a href="/A235871/b235871.txt">Table of n, a(n) for n = 1..5178</a>

%e a(2) = 17 is a prime: 17+2 = 19, 17+24 = 41 and 17+246 = 263 are also prime.

%e a(3) = 107 is a prime: 107+2 = 119, 107+24 = 131 and 107+246 = 353 are also prime.

%p KD:= proc() local a,b,d,e; a:= ithprime(n); b:=a+2;d:=a+24;e:=a+246; if isprime(b) and isprime(d) and isprime(e) then return (a) :fi; end: seq(KD(), n=1..15000);

%t KD = {}; Do[p = Prime[n]; If[PrimeQ[p + 2] && PrimeQ[p + 24] && PrimeQ[p + 246], AppendTo[KD, p]], {n, 15000}]; KD

%t c = 0; p = Prime[n]; Do[If[PrimeQ[p + 2] && PrimeQ[p + 24] && PrimeQ[p + 246], c = c + 1; Print[c, " ", Prime[n]]], {n, 1, 5000000}];  (* b - file *)

%o (PARI) s=[]; forprime(p=2, 50000, if(isprime(p+2) && isprime(p+24) && isprime(p+246), s=concat(s, p))); s \\ _Colin Barker_, Apr 21 2014

%Y Cf. A000040, A023200, A046136, A230223,  A237890.

%K nonn

%O 1,1

%A _K. D. Bajpai_, Apr 21 2014