A049493 - OEIS

%I #18 Mar 26 2024 04:59:15

%S 3,7,37,43,67,163,757,823,967,1087,1213,1303,1423,2293,2377,3187,3343,

%T 3847,5653,5923,8677,8803,9157,9277,9787,11257,11617,11923,12097,

%U 13693,14653,14767,14827,15667,15733,16417,18127,18397,20113,20743,26293

%N Numbers n such that n and n+4^k are all primes for k=1,2,3.

%H Harvey P. Dale, <a href="/A049493/b049493.txt">Table of n, a(n) for n = 1..1000</a>

%F A049492 INTERSECT A049490. - _R. J. Mathar_, Mar 26 2024

%e 3, 3+4=7, 3+16=19, 3+64=67 are all primes.

%t Select[Prime[Range[3000]],And@@PrimeQ[#+4^{1,2,3}]&] (* _Harvey P. Dale_, Dec 26 2013 *)

%o (PARI) isok(n) = isprime(n) && isprime(n+4) && isprime(n+16) && isprime(n+64); \\ _Michel Marcus_, Dec 22 2013

%Y Subsequence of A049492.

%K nonn

%O 1,1

%A _Labos Elemer_