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A023259
Primes that remain prime through 2 iterations of function f(x) = 7x + 6.
4
5, 11, 31, 59, 61, 71, 149, 179, 269, 439, 499, 541, 571, 719, 761, 1049, 1091, 1181, 1319, 1451, 1489, 1579, 1601, 1831, 1861, 1879, 1949, 2069, 2089, 2269, 2311, 2389, 2441, 2621, 2699, 2819, 2851, 2909, 3001, 3079, 3119, 3391, 3529, 3631, 3701, 3709
OFFSET
1,1
COMMENTS
Primes p such that 7*p+6 and 49*p+48 are also primes. - Vincenzo Librandi, Aug 04 2010
FORMULA
a(n) = 1 or 9 (mod 10) for n > 1. - John Cerkan, Sep 14 2016
MATHEMATICA
Select[Prime[Range[600]], AllTrue[Rest[NestList[7#+6&, #, 2]], PrimeQ]&] (* Harvey P. Dale, Jan 26 2024 *)
PROG
(Magma) [n: n in [1..100000] | IsPrime(n) and IsPrime(7*n+6) and IsPrime(49*n+48)] // Vincenzo Librandi, Aug 04 2010
CROSSREFS
Subsequence of A023225, A024900. - John Cerkan, Sep 14 2016
Sequence in context: A052228 A371670 A105910 * A267478 A280081 A057470
KEYWORD
nonn
STATUS
approved