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A138066 Least k>0 such that (2n-1)^k + 2 is prime, or 0 if no such number exists. 4
1, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 11, 0, 1, 1, 0, 2, 1, 0, 1, 1, 0, 1, 113, 0, 1, 7, 0, 1, 1, 0, 3, 1, 0, 1, 1, 0, 12, 1, 0, 1, 3, 0, 1, 255, 0, 8, 1, 0, 1, 1, 0, 1, 1, 0, 1, 3, 0, 2, 15, 0, 2, 1, 0, 1, 23, 0, 1, 1, 0, 4, 3, 0, 1, 1, 0, 3, 1, 0, 136, 1, 0, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,12

COMMENTS

a(3n+1) = 0 for n>0.

a(84) > 100000. [From Ray Chandler, Aug 10 2011]

LINKS

Table of n, a(n) for n=1..83.

CROSSREFS

Cf. A084713 = Smallest prime of the form (2n-1)^k + 2, or 0 if no such number exists. Cf. A138067 = Least k>1 such that (2n-1)^k + 2 is prime, or 0 if no such number exists. Cf. A051783 = Numbers n such that 3^n + 2 is prime. Cf. A087885 = Numbers n such that 5^n + 2 is prime. Cf. A090649, A109076, A113480, A138048, A138049, A138050, A138051, A087886, A113481.

Sequence in context: A216726 A323169 A143197 * A173189 A115595 A187553

Adjacent sequences:  A138063 A138064 A138065 * A138067 A138068 A138069

KEYWORD

hard,nonn

AUTHOR

Alexander Adamchuk, Mar 02 2008

STATUS

approved

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Last modified September 18 05:32 EDT 2019. Contains 327165 sequences. (Running on oeis4.)