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A122721 Numbers n such that abs(7^n - 2^11) is prime. 0
2, 4, 5, 6, 9, 21, 41, 52, 58, 118, 130, 585, 614, 744, 881, 941, 966, 1280, 1658, 4985 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..20.

C. Pomerance, Science News reference.

EXAMPLE

For x = 2 abs(7^2-2^11) = 1999 which is prime. So 2 is the first entry.

PROG

(PARI) g(n) = for(x=1, n, y=abs(7^x-2^11); if(ispseudoprime(y), print1(x", ")))

CROSSREFS

Sequence in context: A003306 A250305 A136585 * A014224 A175342 A077312

Adjacent sequences:  A122718 A122719 A122720 * A122722 A122723 A122724

KEYWORD

easy,nonn

AUTHOR

Cino Hilliard, Sep 23 2006

STATUS

approved

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Last modified July 17 14:44 EDT 2019. Contains 325106 sequences. (Running on oeis4.)