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 A023302 Numbers n such that n remains prime through 4 iterations of function f(x) = 2x + 1. 32
 2, 89, 179, 53639, 53849, 61409, 63419, 66749, 126839, 127139, 143609, 167729, 186149, 206369, 254279, 268049, 296099, 340919, 405269, 422069, 446609, 539009, 594449, 607319, 658349, 671249, 725009, 775949, 810539, 810809, 812849, 819509 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS n, 2*n+1, 4*n+3, 8*n+7 and 16*n+15 are primes. - Vincenzo Librandi, Aug 04 2010 At n > 1, a(n) == 29 mod 30. One should use it in codes. - Zak Seidov, Jan 31 2013 LINKS Harvey P. Dale, Table of n, a(n) for n = 1..1000 MATHEMATICA Select[Prime[Range[10^4*4]], PrimeQ[a1=2*#+1] && PrimeQ[a2=2*a1+1] && PrimeQ[a3=2*a2+1] && PrimeQ[a4=2*a3+1] &] (* Vladimir Joseph Stephan Orlovsky, May 01 2008 *) Join[{2}, Select[Range[29, 820000, 30], And@@PrimeQ[NestList[2#+1&, #, 4]]&]] (* Harvey P. Dale, Apr 03 2013 *) PROG (MAGMA) [n: n in [1..1200000] | IsPrime(n) and IsPrime(2*n+1) and IsPrime(4*n+3) and IsPrime(8*n+7) and IsPrime(16*n+15)] // Vincenzo Librandi, Aug 04 2010 (PARI) is(n)=isprime(n) && isprime(2*n+1) && isprime(4*n+3) && isprime(8*n+7) && isprime(16*n+15) \\ Charles R Greathouse IV, Jul 01 2013 CROSSREFS Cf. A005384, A005385, A007700, A023272, A023330, A057331, A005602. Sequence in context: A161676 A235467 A249305 * A041967 A226768 A246871 Adjacent sequences:  A023299 A023300 A023301 * A023303 A023304 A023305 KEYWORD nonn AUTHOR STATUS approved

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Last modified September 21 03:13 EDT 2020. Contains 337266 sequences. (Running on oeis4.)