A256396 Primes p such that p divides 3*2^k + 1 for some k >= 0.

2, 5, 7, 11, 13, 19, 29, 37, 53, 59, 61, 67, 79, 83, 97, 101, 103, 107, 131, 139, 149, 163, 173, 179, 181, 193, 197, 199, 211, 227, 269, 271, 293, 307, 313, 317, 347, 349, 367, 373, 379, 389, 409, 419, 421, 439, 443, 461, 463, 467, 487, 491, 499, 509, 523, 541, 547, 557, 563, 577, 587

Offset

1,1

Comments

Also prime factors of the numbers 2^k + 3.

Primes in A256397 do not belong to this sequence.

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Formula

A prime p is in the sequence if and only if -3 == 2^k (mod p).

Prog

(PARI) is(n)=if(!isprime(n), return(0)); if(n<5, return(n==2)); my(m=Mod(2, n)); while(m!=1, if(m==-3, return(1), m*=2)); 0 \\ Charles R Greathouse IV, Jun 03 2015

Crossrefs

Supersequence of A039687.

Sequence in context: A293859 A045347 A098170 * A291280 A120330 A023216

Adjacent sequences: A256393 A256394 A256395 * A256397 A256398 A256399

Keyword

nonn

Author

Arkadiusz Wesolowski, Jun 03 2015

Status

approved