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A076845
Least k>0 such that n^k + n - 1 is prime.
4
1, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 2, 16, 1, 1, 4, 3, 1, 2, 1, 1, 4, 1, 3, 2, 1, 2, 10, 1, 1, 108, 3, 1, 2, 1, 1, 2, 2, 1, 2, 1, 3, 2, 1, 2, 20, 2, 1, 2, 1, 1, 2, 1, 1, 2, 1, 4, 2, 2, 7, 8, 3, 1, 2, 1, 24, 2, 1, 1, 12, 4, 3, 8, 1, 1, 4, 3, 1, 194, 3, 1, 2, 1, 2, 2, 1, 8, 2, 1, 1, 4, 2, 2, 54, 1, 1, 4, 1, 1
OFFSET
2,4
MATHEMATICA
lk[n_]:=Module[{k=1}, While[!PrimeQ[n^k+n-1], k++]; k]; Array[lk, 100, 2] (* Harvey P. Dale, Jun 29 2017 *)
PROG
(PARI) a(n) = {my(k=1); while(!isprime(n^k+n-1), k++); k; } \\ Michel Marcus, Nov 29 2013
(Haskell)
a076845 n = head [k | k <- [1..], a010051'' (n ^ k + n - 1) == 1]
-- Reinhard Zumkeller, Jul 17 2014
CROSSREFS
Cf. A010051.
Sequence in context: A111178 A279187 A254434 * A161906 A319135 A338884
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Nov 20 2002
STATUS
approved