cp's OEIS Frontend

A023275 Primes that remain prime through 3 iterations of function f(x) = 2x + 7.

%I A023275 #24 Dec 26 2022 16:36:39
%S A023275 5,23,293,593,953,2063,3323,4133,4583,8243,8783,9173,9203,14723,15383,
%T A023275 16103,16763,18413,19163,20123,25733,29453,37223,38783,39443,40253,
%U A023275 41903,42923,44753,45863,49433,51473,54443,54623,54713,57383,58913,63353,66533
%N A023275 Primes that remain prime through 3 iterations of function f(x) = 2x + 7.
%C A023275 Primes p such that 2*p+7, 4*p+21 and 8*p+49 are also primes. - _Vincenzo Librandi_, Aug 04 2010
%H A023275 John Cerkan, <a href="/A023275/b023275.txt">Table of n, a(n) for n = 1..10000</a>
%F A023275 a(n) == 23 (mod 30) for n > 1. - _John Cerkan_, Sep 16 2016
%t A023275 Select[Prime@ Range@ 7000, Times @@ Boole@ PrimeQ@ Rest@ NestList[2 # + 7 &, #, 3] > 0 &] (* _Michael De Vlieger_, Sep 19 2016 *)
%t A023275 Select[Prime[Range[7000]],AllTrue[Rest[NestList[2#+7&,#,3]],PrimeQ]&] (* _Harvey P. Dale_, Dec 26 2022 *)
%o A023275 (Magma) [n: n in [1..100000] | IsPrime(n) and IsPrime(2*n+7) and IsPrime(4*n+21) and IsPrime(8*n+49)] // _Vincenzo Librandi_, Aug 04 2010
%o A023275 (PARI) is(n)=isprime(n) && isprime(2*n+7) && isprime(4*n+21) && isprime(8*n+49) \\ _Charles R Greathouse IV_, Sep 20 2016
%Y A023275 Subsequence of A023206, A023244, and of A105760.
%K A023275 nonn
%O A023275 1,1
%A A023275 _David W. Wilson_