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A253773
Numbers k such that 4^k + 15 is prime.
2
1, 2, 3, 4, 5, 6, 8, 11, 13, 15, 16, 20, 21, 23, 36, 38, 90, 99, 155, 164, 171, 254, 255, 273, 404, 1386, 1941, 1970, 2420, 3759, 5559, 5776, 6369, 6429, 22061, 32330, 81780, 90248, 162933, 240920, 504584
OFFSET
1,2
COMMENTS
Half of even terms of A057197. - Michel Marcus, Aug 28 2015
EXAMPLE
For k = 15, 4^15 + 15 = 1073741839 is prime.
MATHEMATICA
Select[Range[10000], PrimeQ[4^# + 15] &]
PROG
(Magma) [n: n in [0..1300] | IsPrime(4^n+15)];
(PARI) is(n)=isprime(4^n + 15) \\ Anders Hellström, Aug 28 2015
CROSSREFS
Cf. A057197, A237418, A253772 (similar sequence).
Sequence in context: A046889 A026267 A262527 * A124067 A308806 A060967
KEYWORD
nonn,more
AUTHOR
Vincenzo Librandi, Jan 12 2015
EXTENSIONS
a(31)-a(39) from A057197 data by Michel Marcus, Aug 28 2015
a(40) derived from A057197 by Robert Price, Sep 18 2015
a(41) from A057197 data by Elmo R. Oliveira, Dec 11 2023
STATUS
approved