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A225769 Least k>0 such that k^7+n is prime, or 0 if there is no such k. 1
0, 1, 1, 2, 1, 6, 1, 16, 9, 2, 1, 2, 1, 6, 5, 22, 1, 8, 1, 10, 3, 2, 1, 2, 17, 12, 3, 4, 1, 2, 1, 6, 5, 4, 3, 2, 1, 4, 5, 2, 1, 6, 1, 4, 23, 2, 1, 24, 5, 4, 3, 2, 1, 2, 5, 6, 3, 28, 1, 8, 1, 22, 39, 2, 3, 2, 1, 4, 5, 2, 1, 2, 1, 6, 9, 34, 7, 6, 1, 10, 3, 16, 1, 2, 23, 22, 3, 14, 1, 14, 23, 12, 9, 4, 3, 2, 1, 4, 9, 2, 1, 2, 1, 4, 5, 2, 1, 8, 1, 4, 3, 2, 1, 2, 23, 12, 5, 40, 31, 92, 7 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

See A225768 for motivation and references.

LINKS

Table of n, a(n) for n=0..120.

PROG

(PARI) (a, b=5)->{#factor(x^b+a)~==1&for(n=1, 9e9, ispseudoprime(n^b+a)&return(n)); a==1 || print1("/*"factor(x^b+a)"*/")} \\ For illustrative purpose only. The polynomial is factored to avoid an infinite search loop when it is composite. But a factored polynomial can yield a prime when all factors but one equal 1. This happens for b=4, n=4, cf. A225766.

CROSSREFS

See A085099, A225765--A225770 for the k^2, k^3, ..., k^8 analogs.

Sequence in context: A060173 A059344 A109193 * A280736 A279095 A186283

Adjacent sequences:  A225766 A225767 A225768 * A225770 A225771 A225772

KEYWORD

nonn

AUTHOR

M. F. Hasler, Jul 25 2013

STATUS

approved

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Last modified December 19 11:05 EST 2018. Contains 318246 sequences. (Running on oeis4.)