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A105180 Numbers k such that 2^(2*k+1) + 2^k + 1 is prime. 0

%I

%S 1,2,3,5,9,25,34,36,42,52,176,262,269,283,284,289,372,392,486,596,999,

%T 1022,1097,1105,2329,2663,3037,3363,3853,5167,6305,7164,7283,8874,

%U 10974,14450,14763,15016,15320,24869,27192

%N Numbers k such that 2^(2*k+1) + 2^k + 1 is prime.

%C a(36) > 11800. - _Jinyuan Wang_, Mar 19 2020

%e 2^3 + 2^1 + 1 = 11 prime so a(1) = 1.

%e 2^5 + 2^2 + 1 = 37 prime so a(2) = 2.

%e 2^7 + 2^3 + 1 = 137 prime so a(3) = 3.

%o (PARI) is(n)=ispseudoprime(2^(2*n+1)+2^n+1) \\ _Charles R Greathouse IV_, Jun 13 2017

%K nonn,more

%O 1,2

%A _Pierre CAMI_, Apr 11 2005

%E a(34)-a(35) from _Jinyuan Wang_, Mar 19 2020

%E a(36)-a(41) from _Jeppe Stig Nielsen_, Jun 16 2020

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Last modified February 6 17:09 EST 2023. Contains 360110 sequences. (Running on oeis4.)