A057203 - OEIS

%I #13 Dec 01 2023 19:23:48

%S 3,7,39,79,359,451,1031,1039,11311,30227,47599,55731,307099,351831,

%T 418851

%N Numbers k such that 2^k + 23 is prime.

%C a(16) > 5*10^5. - _Robert Price_, Sep 06 2015

%C All terms are odd. - _Elmo R. Oliveira_, Dec 01 2023

%H Henri Lifchitz and Renaud Lifchitz, <a href="http://www.primenumbers.net/prptop/searchform.php?form=2%5En%2B23">Search for 2^n+23</a>, PRP Top Records.

%e For k = 39, 2^39 + 23 = 549755813911 is prime.

%t Do[ If[ PrimeQ[2^n + 23], Print[ n ]], {n, 1, 5000} ]

%o (PARI) is(n)=isprime(2^n+23) \\ _Charles R Greathouse IV_, Feb 17 2017

%Y Cf. A094076.

%Y Cf. A019434 (primes 2^k+1), A057732 (2^k+3), A059242 (2^k+5), A057195 (2^k+7), A057196(2^k+9), A102633 (2^k+11), A102634 (2^k+13), A057197 (2^k+15), A057200 (2^k+17), A057221 (2^k+19), A057201 (2^k+21), this sequence (2^k+23).

%K nonn,more

%O 1,1

%A _Robert G. Wilson v_, Sep 16 2000

%E a(9)-a(15) from _Robert Price_, Sep 06 2015