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A178250 Least number x such that n^x-n-1 is prime. 1
3, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 4, 2, 3, 2, 2, 3, 5, 2, 2, 2, 3, 3, 2, 4, 2, 5, 2, 5, 2, 2, 7, 5, 3, 2, 9, 3, 2, 2, 3, 2, 31, 4, 2, 2, 2, 3, 2, 4, 2, 108, 4, 2, 2, 2, 2, 3, 3, 2, 2, 18, 7, 3, 2, 2, 2, 4, 2, 3, 2, 5, 32, 108, 5, 3, 2, 11, 4, 15, 3, 4, 19, 2, 6, 2, 2, 11, 107, 2, 42, 4, 39, 2, 2, 6, 2, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

COMMENTS

Least number x such that x^n-x-1 is prime see A127599.

LINKS

Table of n, a(n) for n=2..98.

MATHEMATICA

a = {}; Do[k = 2; While[ ! PrimeQ[n^k - n - 1], k++ ]; AppendTo[a, k], {n, 2, 500}]; a (*Artur Jasinski*)

lnx[n_]:=Module[{x=1}, While[!PrimeQ[n^x-n-1], x++]; x]; Array[lnx, 100, 2] (* Harvey P. Dale, Jul 09 2017 *)

CROSSREFS

Cf. A127599

Sequence in context: A252503 A270003 A067438 * A174550 A119704 A104223

Adjacent sequences:  A178247 A178248 A178249 * A178251 A178252 A178253

KEYWORD

nonn

AUTHOR

Artur Jasinski, May 24 2010

STATUS

approved

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Last modified September 19 11:06 EDT 2019. Contains 327192 sequences. (Running on oeis4.)