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%I #26 Mar 29 2023 04:53:16
%S 1,3,7,9,15,21,33,37,61,141,159,229,345,373,511,717,2065,2337,15619,
%T 22771,22875,23911,29323,53025
%N Numbers k such that 2^k + 5*k is a prime.
%C a(19) = 15619 corresponds to a probable prime. - _Jon E. Schoenfield_, Feb 28 2018
%p a:=n->`if`(isprime(2^n+5*n),n,NULL): seq(a(n),n=1..7000); # _Muniru A Asiru_, Mar 10 2018
%t Select[Range[7000], PrimeQ[2^# + 5 #] &]
%o (Magma) [n: n in [0..2000] |IsPrime(2^n+5*n)];
%o (PARI) isok(k) = isprime(2^k + 5*k); \\ _Altug Alkan_, Mar 03 2018
%Y Cf. A297663.
%K nonn,more
%O 1,2
%A _Vincenzo Librandi_, Feb 28 2018
%E a(19) from _Jon E. Schoenfield_, Feb 28 2018
%E a(20)-a(23) from _Daniel Suteu_, Mar 11 2018
%E a(24) from _Michael S. Branicky_, Mar 28 2023
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