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A225392 Numbers b such that b^(2^n) + 2 is prime for n from 0 to 4. 0
22155, 1864149, 2760681, 6222765, 22687797, 25631319, 29309589, 33333069, 36490905, 56310891, 60212889, 74097849, 76008207, 80864685, 84214395, 132006225, 132621171, 137362521, 138993381, 152223885, 154185525, 175950081, 188261481, 188677335, 194279955 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Generalized Fermat numbers of the form b^(2^n) + k with k = 2 here.

For b = 2760681, b^(2^n) + 2 is prime for n from 0 to 5

LINKS

Table of n, a(n) for n=1..25.

PROG

(PARI) k=2; forstep(b=1, 5*10^7, [4, 2, 2, 2], i=0; for(n=0, 4, m=b^2^n+k; if(isprime(m), i++; if(i>4, print([b, m, n, i])))))

CROSSREFS

Cf. A070694, A225321

Sequence in context: A043590 A043815 A157622 * A225998 A209396 A210295

Adjacent sequences:  A225389 A225390 A225391 * A225393 A225394 A225395

KEYWORD

nonn

AUTHOR

Robin Garcia, May 06 2013

EXTENSIONS

a(10)-a(25) from Giovanni Resta, May 06 2013

STATUS

approved

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Last modified September 20 01:58 EDT 2019. Contains 327207 sequences. (Running on oeis4.)