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A023248 Numbers n such that n remains prime through 2 iterations of function f(x) = 3x + 8. 4
3, 11, 13, 31, 41, 43, 53, 101, 113, 211, 223, 263, 283, 431, 433, 491, 521, 563, 571, 601, 631, 641, 673, 743, 811, 911, 1151, 1361, 1621, 1693, 1973, 2243, 2393, 3083, 3163, 3181, 3343, 3461, 3821, 3923, 4481, 4523, 4561, 4591, 4663, 4861, 4903, 5051, 5261 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers n such that n, 3*n+8, and 9*n+32 are primes. - Vincenzo Librandi, Aug 04 2010

LINKS

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

FORMULA

a(n) == 1 or 3 (mod 10) for n>=2. - John Cerkan, Sep 13 2016

MATHEMATICA

Select[Range@ 5280, Times @@ Boole@ PrimeQ@ NestList[3 # + 8 &, #, 2] > 0 &] (* Michael De Vlieger, Sep 13 2016 *)

PROG

(MAGMA) [n: n in [0..100000] | IsPrime(n) and IsPrime(3*n+8) and IsPrime(9*n+32)] // Vincenzo Librandi, Aug 04 2010

CROSSREFS

Subsequence of A023210.

Sequence in context: A033680 A032917 A006559 * A199341 A111488 A125308

Adjacent sequences:  A023245 A023246 A023247 * A023249 A023250 A023251

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved

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Last modified November 22 16:31 EST 2019. Contains 329396 sequences. (Running on oeis4.)