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A023322
Primes that remain prime through 4 iterations of function f(x) = 8x + 7.
2
7949, 25589, 55799, 61379, 69959, 70229, 74609, 174569, 188369, 204719, 220469, 225629, 233759, 250919, 286619, 363659, 552749, 592139, 658349, 735419, 783269, 827549, 931949, 1018889, 1065839, 1126319, 1132739, 1187939, 1215629, 1378529
OFFSET
1,1
COMMENTS
Primes p such that 8*p+7, 64*p+63, 512*p+511 and 4096*p+4095 are also primes. - Vincenzo Librandi, Aug 04 2010
FORMULA
a(n) == 9 (mod 10). - John Cerkan, Oct 08 2016
MATHEMATICA
rp4Q[p_]:=AllTrue[Rest[NestList[8#+7&, p, 4]], PrimeQ]; Select[Prime[Range[110000]], rp4Q] (* Harvey P. Dale, Aug 03 2023 *)
PROG
(Magma) [n: n in [1..5000000] | IsPrime(n) and IsPrime(8*n+7) and IsPrime(64*n+63) and IsPrime(512*n+511) and IsPrime(4096*n+4095)] // Vincenzo Librandi, Aug 04 2010
CROSSREFS
Subsequence of A023231, A023263, A023294, and A139487.
Sequence in context: A302901 A179708 A162010 * A064246 A260959 A316906
KEYWORD
nonn
STATUS
approved