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A269834 Primes p of the form 2^n + 9*(-1)^n - 8. 0

%I #7 Sep 08 2022 08:46:16

%S 2,5,17,257,65537

%N Primes p of the form 2^n + 9*(-1)^n - 8.

%C Union of number 2 and Fermat primes > 3 from A019434; for odd n, numbers 2^n - 17 are divisible by 3.

%C Also primes p of the form 2^n + 12*(-1)^n - 11 for n >= 0 because for odd n, numbers 2^n - 23 are divisible by 3.

%C Also primes p of the form 2^n + 1/2*(q + 1)*(-1)^n - 1/2*(q - 1) for n >= 0 where q = prime of the form 3m - 1 > 29 from A003627 because for odd n, numbers 2^n - q are divisible by 3.

%C Corresponding values of n: 0, 2, 4, 8, 16, ...

%o (Magma) [2^n + 9*(-1)^n - 8: n in [0..1000] | IsPrime(2^n + 9*(-1)^n - 8)]

%Y Sequence is different from A132198 and A111635.

%Y Cf. A003627, A019434.

%K nonn

%O 1,1

%A _Jaroslav Krizek_, Mar 06 2016

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Last modified April 20 02:01 EDT 2024. Contains 371798 sequences. (Running on oeis4.)