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%I #49 Sep 15 2022 09:20:11
%S 2,3,4,7,9,10,16,31,45,54,64,261,304,640,1102,1141,1609,2127,2212,
%T 4845,4971,5607,9969,10851,11605,22249,43122,55252,66025,108046,
%U 378420,429717,628894,699135,1488111,1510689,3486297,6733459,10498006,12018292,12982476,15201229,16291329,18578334
%N Numbers k such that 2^(2*k - 1) - 1 is prime.
%H Mario García, <a href="/A138576/b138576.txt">Table of n, a(n) for n = 1..50</a>
%F a(n) = (A000043(n+1) + 1)/2. - _Charles R Greathouse IV_, Aug 30 2010
%F a(n) = A146768(n) + 1. - _César Aguilera_, May 27 2020
%e 2^(2*2 - 1) - 1 = 7;
%e 2^(2*3 - 1) - 1 = 31;
%e 2^(2*4 - 1) - 1 = 127.
%o (PARI) is(n)=isprime(2^(2*n-1)-1) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y Cf. A000043, A146768.
%K nonn,easy
%O 1,1
%A _Vladimir Joseph Stephan Orlovsky_, May 13 2008
%E More terms from _Charles R Greathouse IV_, Aug 30 2010
%E More terms from _Mario García_, Jul 18 2022
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