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%I #22 Jul 27 2024 09:39:52
%S 1,3,5,11,13,61,115,653,889,957,997,1013,1421,2329,2675,4795,5755,
%T 7059,7405,7613,7973,9445,23467,31769,32417,74875,83029,85173
%N Numbers k such that 7*2^k + 5 is prime.
%C a(24) > 30000. - _Jinyuan Wang_, Feb 01 2020
%t Do[ If[ PrimeQ[ 7*2^n + 5 ], Print[ n ] ], {n, 1, 6800} ]
%t Select[Range[0, 10000], PrimeQ[(7*2^# + 5)] &] (* _Vincenzo Librandi_, Sep 29 2012 *)
%o (PARI) is(n)=ispseudoprime(7*2^n+5) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y Cf. A058602 (7*2^k - 5 is prime).
%K nonn,more
%O 1,2
%A _Robert G. Wilson v_, Dec 26 2000
%E a(18)-a(22) from _Vincenzo Librandi_, Sep 29 2012
%E a(23) from _Jinyuan Wang_, Feb 01 2020
%E a(24)-a(25) from _Michael S. Branicky_, May 19 2023
%E a(26)-a(28) from _Michael S. Branicky_, Jul 27 2024