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Numbers k such that 2^k - 15 is prime.
14

%I #42 Nov 16 2023 15:56:28

%S 5,7,8,10,14,16,23,76,95,100,158,196,235,338,620,1646,1850,1891,3833,

%T 4394,5194,6017,6070,8824,9955,11399,12250,28723,32057,45494,137359,

%U 139627,160654,178819,183284,276391,283466,400571,449030,632815,875518,981016,3511529

%N Numbers k such that 2^k - 15 is prime.

%H Henri Lifchitz and Renaud Lifchitz, <a href="http://www.primenumbers.net/prptop/searchform.php?form=2%5En-15">Search for 2^n-15</a>, PRP Top Records.

%e 100 is present because 2^100 - 15 is prime.

%p A059612:=n->if isprime(2^n-15) then n; fi; seq(A059612(n), n=1..20000); # _Wesley Ivan Hurt_, Dec 06 2013

%t Select[Range[4,20000],PrimeQ[2^#-15]&] (* _Vladimir Joseph Stephan Orlovsky_, Feb 27 2011 *)

%o (PARI) is(n)=isprime(2^n-15) \\ _Charles R Greathouse IV_, Feb 17 2017

%Y Cf. A096502.

%Y Cf. Sequences of numbers k such that 2^k - d is prime: A000043 (d=1), A050414 (d=3), A059608 (d=5), A059609 (d=7), A059610 (d=9), A096817 (d=11), A096818 (d=13), this sequence (d=15), A059611 (d=17), A096819 (d=19), A096820 (d=21), A057220 (d=23), A356826 (d=29).

%K nonn

%O 1,1

%A _Andrey V. Kulsha_, Feb 13 2001

%E a(26) from _Labos Elemer_, Jul 09 2004

%E a(27)-a(29) from _Max Alekseyev_, a(30) from _Henri Lifchitz_, a(31)-a(32) from _Gary Barnes_, a(33)-a(35) from Lelio R Paula, added by _Max Alekseyev_, Feb 09 2012

%E a(36)-a(37) from Lelio R Paula, added by _Max Alekseyev_, Oct 24 2013

%E a(38) from Lelio R Paula, added by _Robert Price_, Dec 06 2013

%E a(39) from Lelio R Paula, added by _Robert Price_, Mar 16 2019

%E a(40)-a(43) from Stefano Morozzi, added by _Elmo R. Oliveira_, Nov 16 2023