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A056208 Primes p+2^n arising in A056206. 10


%S 3,5,7,11,19,37,67,131,263,523,1031,2053,4099,8209,16421,32771,65539,

%T 131101,262147,524341,1048583,2097169,4194371,8388619,16777259,

%U 33554473,67108961,134217757,268435459,536870923,1073741827,2147483659

%N Primes p+2^n arising in A056206.

%H Robert Israel, <a href="/A056208/b056208.txt">Table of n, a(n) for n = 0..2000</a>

%e n=13, 2^13+p=8192+p is not prime for p=2,3,5,7,11,13. At first, for p=17, 8209 is prime; Primes obtained also for many larger p, the next is 8221. So a(13)=8209, the smallest one.

%p f:= proc(n) local p,q,t;

%p t:= 2^n; p:= 1;

%p do

%p p:= nextprime(p);

%p q:= p+t;

%p if isprime(q) then return q fi

%p od

%p end proc:

%p map(f, [$0..50]); # _Robert Israel_, Aug 22 2019

%t a[n_] := Module[{p = 1, q, t = 2^n}, While[True, p = NextPrime[p]; q = p+t; If[PrimeQ[q], Return[q]]]];

%t a /@ Range[0, 50] (* _Jean-Fran├žois Alcover_, Jun 09 2020, after Maple *)

%Y Cf. A056206.

%K nonn

%O 0,1

%A _Labos Elemer_, Oct 06 2000

%E a(0)=3 inserted by _Robert Israel_, Aug 22 2019

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Last modified July 11 17:24 EDT 2020. Contains 335626 sequences. (Running on oeis4.)