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A138067
Least k > 1 such that (2n-1)^k + 2 is prime, or 0 if no such number exists.
2
2, 2, 3, 0, 2, 5, 0, 2, 105, 0, 2, 11, 0, 5, 3, 0, 2, 15, 0, 2, 9, 0, 2, 113, 0, 5, 7, 0, 2, 27, 0, 3, 3, 0, 3, 3, 0, 12, 61, 0, 2, 3, 0, 4, 255, 0, 8, 63, 0, 2, 9, 0, 2, 3473, 0, 2, 3, 0, 2, 15, 0, 2, 87, 0, 3, 23, 0, 36, 1861, 0, 4, 3, 0, 2, 5, 0, 3, 7, 0, 136, 425, 0, 11
OFFSET
1,1
COMMENTS
a(3n+1) = 0 for n > 0.
a(84) > 100000. - Ray Chandler, Aug 10 2011
CROSSREFS
Cf. A084713 (smallest prime of the form (2n-1)^k + 2, or 0 if no such number exists).
Cf. A138066 (least k > 0 such that (2n-1)^k + 2 is prime, or 0 if no such number exists).
Cf. A051783 (k such that 3^k + 2 is prime).
Cf. A087885 (k such that 5^k + 2 is prime).
Sequence in context: A307356 A091426 A053761 * A324348 A125093 A294898
KEYWORD
hard,nonn
AUTHOR
Alexander Adamchuk, Mar 02 2008
EXTENSIONS
a(54)-a(83) from Donovan Johnson, Oct 29 2008
STATUS
approved