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A023255 Numbers n such that n remains prime through 2 iterations of the function f(x) = 5x + 8. 4
7, 13, 19, 31, 43, 73, 211, 223, 241, 307, 397, 409, 631, 661, 727, 757, 769, 829, 883, 1123, 1741, 1783, 1867, 2131, 2143, 2269, 2287, 2467, 2521, 2551, 2857, 2917, 3253, 3319, 3793, 3967, 4297, 4423, 4597, 4957, 5449, 5563, 5701, 6229, 6427, 6469, 6679 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers n such that n, 5*n+8, and 25*n+48 are primes. - Vincenzo Librandi, Aug 04 2010

LINKS

John Cerkan, Table of n, a(n) for n = 1..10000

FORMULA

a(n) == 1 mod 6. - John Cerkan, Sep 14 2016

MATHEMATICA

fQ[n_]:=And@@PrimeQ[NestList[5#+8&, n, 2]]; Select[Range[7000], fQ] (* Harvey P. Dale, Mar 25 2013 *)

PROG

(MAGMA) [n: n in [0..100000] | IsPrime(n) and IsPrime(5*n+8) and IsPrime(25*n+48)] // Vincenzo Librandi, Aug 04 2010

CROSSREFS

Subsequence of A023220, A111225.

Sequence in context: A216550 A267803 A240971 * A122482 A265629 A283191

Adjacent sequences:  A023252 A023253 A023254 * A023256 A023257 A023258

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved

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Last modified June 20 17:27 EDT 2019. Contains 324234 sequences. (Running on oeis4.)