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A023313 Numbers n such that n remains prime through 4 iterations of function f(x) = 5x + 2. 4
373, 1171, 13687, 21997, 25657, 61603, 74413, 76471, 84199, 87181, 93487, 114691, 135859, 170761, 174877, 184333, 192979, 196177, 207931, 209743, 244219, 276229, 286687, 292561, 297811, 334603, 338893, 405037, 408361, 417097, 439141, 446323 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

n, 5*n+2, 25*n+12, 125*n+62 and 625*n+312 are primes. - Vincenzo Librandi, Aug 04 2010

Numbers n such that A280720(n) > 3. - Felix Fröhlich, Jan 07 2017

LINKS

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

FORMULA

a(n) == 31 or 37 (mod 42). - John Cerkan, Oct 07 2016

MATHEMATICA

Select[Range[10^6], Times @@ Boole@ Map[PrimeQ, NestList[5 # + 2 &, #, 4]] == 1 &] (* Michael De Vlieger, Jan 09 2017 *)

PROG

(MAGMA) [n: n in [1..1000000] | IsPrime(n) and IsPrime(5*n+2) and IsPrime(25*n+12) and IsPrime(125*n+62) and IsPrime(625*n+312)] // Vincenzo Librandi, Aug 04 2010

CROSSREFS

Cf. A280720. Subsequence of A023217, A023252, A023283, and A111223.

Sequence in context: A263724 A133559 A229499 * A213301 A213300 A219444

Adjacent sequences:  A023310 A023311 A023312 * A023314 A023315 A023316

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved

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Last modified September 22 10:23 EDT 2020. Contains 337289 sequences. (Running on oeis4.)