A253773 - OEIS

A253773

Numbers k such that 4^k + 15 is prime.

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

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OFFSET

1,2

COMMENTS

Half of even terms of A057197. - Michel Marcus, Aug 28 2015

LINKS

Table of n, a(n) for n=1..41.

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

Adjacent sequences: A253770 A253771 A253772 * A253774 A253775 A253776

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