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 A256396 Primes p such that p divides 3*2^k + 1 for some k >= 0. 2
 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 (list; graph; refs; listen; history; text; internal format)
 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

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Last modified October 16 23:50 EDT 2019. Contains 328103 sequences. (Running on oeis4.)