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A023326 Numbers n such that n remains prime through 4 iterations of the function f(x) = 9x + 8. 2
397, 467, 907, 1747, 1901, 4099, 7237, 8117, 8581, 9371, 9587, 23539, 28081, 32611, 36899, 41729, 54767, 55207, 57601, 61991, 64997, 66449, 73061, 74821, 75527, 86291, 115021, 118717, 125659, 126067, 134287, 140677, 147011, 148147, 151531, 171539 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

n, 9*n+8, 81*n+80, 729*n+728 and 6561*n+6560 are primes. - Vincenzo Librandi, Aug 04 2010

LINKS

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

MATHEMATICA

Select[Prime[Range[16000]], AllTrue[Rest[NestList[9#+8&, #, 4]], PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Jun 25 2017 *)

PROG

(MAGMA) [n: n in [1..5000000] | IsPrime(n) and IsPrime(9*n+8) and IsPrime(81*n+80) and IsPrime(729*n+728) and IsPrime(6561*n+6560)] // Vincenzo Librandi, Aug 04 2010

CROSSREFS

Subsequence of A023235, A023267, and A023298.

Sequence in context: A203926 A270842 A074483 * A139385 A142372 A038660

Adjacent sequences:  A023323 A023324 A023325 * A023327 A023328 A023329

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved

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Last modified July 21 19:25 EDT 2019. Contains 325199 sequences. (Running on oeis4.)