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Primes that remain prime through 4 iterations of function f(x) = 3x + 8.
2

%I #24 Sep 08 2022 08:44:47

%S 3181,9551,22051,30941,32621,61981,76651,99961,134291,151901,163661,

%T 185951,226691,227671,240551,288191,342821,374501,394411,402881,

%U 423781,426301,446461,456151,459091,460951,554011,572321,577601,617191,653831

%N Primes that remain prime through 4 iterations of function f(x) = 3x + 8.

%C Primes p such that 3*p+8, 9*p+32, 27*p+104 and 81*p+320 are also primes. - _Vincenzo Librandi_, Aug 04 2010

%H John Cerkan, <a href="/A023309/b023309.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) == 1 or 31 (mod 70). - _John Cerkan_, Oct 04 2016

%t okQ[n_]:=And@@PrimeQ/@Rest[NestList[3#+8&,n,4]]; Select[Prime[Range[60000]],okQ] (* _Harvey P. Dale_, Aug 16 2010 *)

%o (Magma) [n: n in [1..1000000] | IsPrime(n) and IsPrime(3*n+8) and IsPrime(9*n+32) and IsPrime(27*n+104) and IsPrime(81*n+320)] // _Vincenzo Librandi_, Aug 04 2010

%Y Subsequence of A023210, A023248, and A023279.

%K nonn

%O 1,1

%A _David W. Wilson_