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%I #28 Sep 08 2022 08:44:47
%S 7,41,43,47,67,71,97,103,137,263,293,307,397,421,467,491,571,587,593,
%T 683,727,757,883,907,1021,1061,1063,1097,1153,1373,1427,1433,1453,
%U 1523,1567,1657,1747,1811,1867,2141,2251,2281,2287,2647,2693,2791,2797,2857,2927
%N Primes that remain prime through 2 iterations of function f(x) = 4x + 9.
%C Primes p such that 4*p+9 and 16*p+45 are also primes. - _Vincenzo Librandi_, Aug 04 2010
%H John Cerkan, <a href="/A023251/b023251.txt">Table of n, a(n) for n = 1..10000</a>
%t rpQ[n_]:=AllTrue[Rest[NestList[4#+9&,n,2]],PrimeQ]; Select[Prime[ Range[ 500]],rpQ] (* The program uses the AllTrue function from Mathematica version 10 *) (* _Harvey P. Dale_, May 03 2019 *)
%o (Magma) [n: n in [0..100000] | IsPrime(n) and IsPrime(4*n+9) and IsPrime(16*n+45)] // _Vincenzo Librandi_, Aug 04 2010
%Y Subsequence of A111199.
%K nonn
%O 1,1
%A _David W. Wilson_
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