

A050539


Numbers k such that 27*2^k1 is prime.


5



1, 2, 4, 5, 8, 10, 14, 28, 37, 38, 70, 121, 122, 160, 170, 253, 329, 362, 454, 485, 500, 574, 892, 962, 1213, 1580, 2642, 2708, 4505, 8152, 11858, 13300, 15041, 16118, 16778, 19069, 22769, 29020, 30298, 30377, 35942, 42817, 42869, 62024, 74629, 90449, 91042, 117901, 128594, 143330, 152530, 157898, 175852, 340682, 444622, 627794, 729314, 777992, 1108214, 1163629, 1253870
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OFFSET

1,2


COMMENTS

3855094, 4542344 and 4583717 are also in the sequence.  Felix Fröhlich, Sep 19 2014


LINKS

Table of n, a(n) for n=1..61.
Ray Ballinger and Wilfrid Keller, List of primes k.2^n + 1 for k < 300
Wilfrid Keller, List of primes k.2^n  1 for k < 300
Kosmaj, Riesel list k<300.
PrimeGrid, Announcement of n=3855094 , Announcement of n=4542344, Announcement of n=4583717  Felix Fröhlich, Sep 19 2014
Index entries for sequences of n such that k*2^n1 (or k*2^n+1) is prime


MATHEMATICA

For[n = 1, n <= 10000, n++, If[PrimeQ[27*2^n  1], Print[n]]] (* Wesley Ivan Hurt, May 19 2014 *)
Select[Range[1000], PrimeQ[27*2^#  1] & ] (* Robert Price, Dec 22 2018 *)


PROG

(PARI) a(n)=if(ispseudoprime(27*2^n1), print1(n, ", ")) \\ Felix Fröhlich, Sep 19 2014


CROSSREFS

Cf. A032363 = 27*2^n+1 is prime.
Sequence in context: A163295 A101274 A080222 * A277101 A039895 A300351
Adjacent sequences: A050536 A050537 A050538 * A050540 A050541 A050542


KEYWORD

hard,nonn


AUTHOR

N. J. A. Sloane, Dec 29 1999


EXTENSIONS

More terms from Hugo Pfoertner, Aug 17 2004
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
a(59)a(61) from the Wilfrid Keller link by Robert Price, Dec 22 2018


STATUS

approved



