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A023256 Numbers n such that n remains prime through 2 iterations of function f(x) = 6x + 1. 3
2, 17, 47, 61, 101, 131, 151, 331, 367, 461, 607, 751, 937, 971, 1151, 1321, 1327, 1361, 1481, 1511, 1607, 1811, 1847, 1907, 2081, 2287, 2347, 2357, 2791, 2851, 2971, 3251, 3257, 3457, 3491, 3581, 3761, 4007, 4091, 4127, 4861, 4967, 5231, 5347, 5387, 5407 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers n such that n, 6*n+1, 36*n+7 are primes. - Vincenzo Librandi, Aug 04 2010

Subsequence of A007693. - Michel Marcus, Oct 17 2015

LINKS

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

FORMULA

a(n) == 1 or 7 (mod 10) for n > 1. - John Cerkan, Sep 14 2016

PROG

(MAGMA) [n: n in [0..100000] | IsPrime(n) and IsPrime(6*n+1) and IsPrime(36*n+7)] // Vincenzo Librandi, Aug 04 2010

(PARI) lista(nn) = forprime(n=1, nn, if (isprime(p=6*n+1) && isprime(6*p+1), print1(n, ", "))); \\ Michel Marcus, Oct 17 2015

CROSSREFS

Cf. A007693.

Sequence in context: A046973 A226488 A134784 * A073775 A141860 A105691

Adjacent sequences:  A023253 A023254 A023255 * A023257 A023258 A023259

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved

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Last modified June 16 21:20 EDT 2019. Contains 324155 sequences. (Running on oeis4.)