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%I #28 Sep 25 2021 06:49:11
%S 7,11,13,23,29,41,47,53,59,83,89,97,107,113,137,149,167,173,179,193,
%T 227,233,263,269,293,317,347,353,359,383,389,449,467,479,503,509,557,
%U 563,569,587,593,641,653,719,769,773,797,809,839,857,863,887,929,977
%N Primes of the form p*2^k + 1, where p is an odd prime and k > 0.
%H Amiram Eldar, <a href="/A058500/b058500.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..2000 from T. D. Noe)
%e 719 is a term because 719 = 2*359 + 1 and 359 is prime.
%t mx = 1000; Select[ Sort@ Flatten@ Table[Prime[p] 2^k + 1, {p, 2, PrimePi[ mx/2]}, {k, Log2[ mx/Prime[ p]]}], PrimeQ] (* or *)
%t fQ[n_] := Block[{m = n -1}, PrimeQ[m/2^IntegerExponent[m, 2]]]; Select[
%t Prime@ Range@ PrimePi@ mx, fQ] (* _Robert G. Wilson v_, Feb 09 2018 *)
%o (PARI) isoka(p) = isprime(p) && (pp=p-1) && isprime(pp/2^valuation(pp, 2)); \\ _Michel Marcus_, Feb 09 2018
%Y Cf. A057023, A006093.
%Y Cf. A074781 (this sequence and the Fermat primes), A147545.
%K nonn
%O 1,1
%A _Labos Elemer_, Dec 20 2000
%E Revised definition from _T. D. Noe_, Nov 03 2008
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