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A023275
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Primes that remain prime through 3 iterations of function f(x) = 2x + 7.
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3
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5, 23, 293, 593, 953, 2063, 3323, 4133, 4583, 8243, 8783, 9173, 9203, 14723, 15383, 16103, 16763, 18413, 19163, 20123, 25733, 29453, 37223, 38783, 39443, 40253, 41903, 42923, 44753, 45863, 49433, 51473, 54443, 54623, 54713, 57383, 58913, 63353, 66533
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OFFSET
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1,1
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COMMENTS
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Primes p such that 2*p+7, 4*p+21 and 8*p+49 are also primes. - Vincenzo Librandi, Aug 04 2010
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LINKS
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FORMULA
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a(n) == 23 (mod 30) for n > 1. - John Cerkan, Sep 16 2016
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MATHEMATICA
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Select[Prime@ Range@ 7000, Times @@ Boole@ PrimeQ@ Rest@ NestList[2 # + 7 &, #, 3] > 0 &] (* Michael De Vlieger, Sep 19 2016 *)
Select[Prime[Range[7000]], AllTrue[Rest[NestList[2#+7&, #, 3]], PrimeQ]&] (* Harvey P. Dale, Dec 26 2022 *)
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PROG
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(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
(PARI) is(n)=isprime(n) && isprime(2*n+7) && isprime(4*n+21) && isprime(8*n+49) \\ Charles R Greathouse IV, Sep 20 2016
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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