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A250200
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Least number k>1 such that (2n-1)^k - 2 is prime, or 0 if no such number exists.
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3
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0, 2, 2, 2, 2, 4, 2, 2, 6, 2, 2, 24, 7, 2, 2, 3, 2, 2, 2, 4, 4, 2, 11, 2, 2, 8, 4, 2, 12, 4, 2, 2, 8, 3, 2, 2, 4, 2, 2, 38, 130, 4, 4, 4, 2, 3, 2, 4, 747, 3, 4, 2, 10, 2, 3, 17, 10, 13, 2, 2, 2, 6, 42, 2, 3, 2, 6, 2, 10, 2, 4, 4, 2, 16, 50, 3, 9, 2, 22, 25
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OFFSET
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1,2
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LINKS
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Robert Price, Table of n, a(n) for n = 1..143
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MATHEMATICA
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lst = {0}; For[n = 2, n ≤ 143, n++, For[k = 2, k >= 1, k++, If[PrimeQ[(2*n - 1)^k - 2], AppendTo[lst, k]; Break[]]]]; lst
lnk[n_]:=Module[{k=2, c=2n-1}, While[!PrimeQ[c^k-2], k++]; k]; Join[{0}, Array[ lnk, 80, 2]] (* Harvey P. Dale, Jul 24 2017 *)
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CROSSREFS
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Cf. A084712, A084713, A084714, A079706, A138066, A255707.
Sequence in context: A349355 A353589 A237709 * A097859 A028326 A156046
Adjacent sequences: A250197 A250198 A250199 * A250201 A250202 A250203
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KEYWORD
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nonn
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AUTHOR
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Robert Price, Mar 02 2015
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STATUS
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approved
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