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A057195 Numbers n such that 2^n + 7 is prime. 17

%I

%S 2,4,6,8,10,16,18,20,28,30,38,44,78,88,98,126,160,174,204,214,588,610,

%T 798,926,1190,1198,1806,1888,2648,3454,3510,3864,3870,8970,12330,

%U 13330,18876,22338,39718,55006,110784,172470,196434,235710,247280,268408,279320,300874,315268,372950,566496

%N Numbers n such that 2^n + 7 is prime.

%C Naturally all terms are even because (3-1)^(2n+1)+7 is divisible by 3. - _Bruno Berselli_, Oct 03 2012

%H Keith Conrad, <a href="https://kconrad.math.uconn.edu/blurbs/ugradnumthy/squaresandinfmanyprimes.pdf">Square patterns and infinitude of primes</a>, University of Connecticut, 2019.

%p A057195:=n->if isprime(2^n+7) then n; fi; seq(A057195(n), n=1..1000); # _Wesley Ivan Hurt_, Dec 06 2013

%t Do[ If[ PrimeQ[ 2^n +7 ], Print[n]], { n, 1, 15000 }]

%o (PARI) is(n)=isprime(2^n+7) \\ _Charles R Greathouse IV_, Feb 17 2017

%Y Cf. A104066 (primes of the form 2^n+7).

%K nonn

%O 1,1

%A _Robert G. Wilson v_, Sep 15 2000

%E a(37)-a(51) from _Robert Price_, Dec 06 2013

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Last modified May 8 11:51 EDT 2021. Contains 343666 sequences. (Running on oeis4.)