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 A023273 Numbers n such that n remains prime through 3 iterations of function f(x) = 2x + 3. 2
 2, 5, 47, 67, 97, 137, 197, 277, 307, 607, 617, 1307, 1427, 2857, 5717, 6047, 6217, 6257, 6997, 9377, 9787, 9967, 11197, 12097, 13297, 13997, 14347, 16057, 18757, 18947, 20887, 21517, 21587, 21757, 24197, 26227, 28097, 28447, 32117, 33767, 34367, 35117 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Primes p such that 2*p+3, 4*p+9 and 8*p+21 are also prime. [Vincenzo Librandi, Aug 04 2010] LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 MATHEMATICA Select[Prime[Range[5000]], AllTrue[Rest[NestList[2#+3&, #, 3]], PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Mar 01 2016 *) PROG (MAGMA) [p: p in PrimesUpTo(50000) | IsPrime(2*p+3) and IsPrime(4*p+9) and IsPrime(8*p+21)]; // Vincenzo Librandi, Aug 04 2010 (Python) from sympy import prime, isprime A023273_list = [p for p in (prime(n) for n in range(1, 10**2)) if isprime(2*p+3) and isprime(4*p+9) and isprime(8*p+21)] # Chai Wah Wu, Sep 09 2014 (PARI) isok(n)=isprime(n) && isprime(2*n+3) && isprime(4*n+9) && isprime(8*n+21) \\ Edward Jiang, Sep 09 2014 CROSSREFS Sequence in context: A225147 A119715 A326965 * A041729 A078665 A163666 Adjacent sequences:  A023270 A023271 A023272 * A023274 A023275 A023276 KEYWORD nonn AUTHOR STATUS approved

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Last modified September 25 15:49 EDT 2020. Contains 337344 sequences. (Running on oeis4.)