A057203 Numbers k such that 2^k + 23 is prime.

3, 7, 39, 79, 359, 451, 1031, 1039, 11311, 30227, 47599, 55731, 307099, 351831, 418851

Offset: 1

Author

Robert G. Wilson v, Sep 16 2000

Keywords

• nonn
• more

Comments

a(16) > 5*10^5. - Robert Price, Sep 06 2015

All terms are odd. - Elmo R. Oliveira, Dec 01 2023

Examples

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

Links

• Henri Lifchitz and Renaud Lifchitz, Search for 2^n+23, PRP Top Records.

Crossrefs

Cf. A094076.

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).

Programs

Mathematica

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

PARI

is(n)=isprime(2^n+23) \\ Charles R Greathouse IV, Feb 17 2017

Extensions

a(9)-a(15) from Robert Price, Sep 06 2015