A076845 Least k>0 such that n^k + n - 1 is prime.
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
Keywords
Links
- Robert Israel, Incomplete table of n, a(n) for n = 2 .. 1000. -1 denotes a value that is > 3000 if it exists.
Programs
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Haskell
a076845 n = head [k | k <- [1..], a010051'' (n ^ k + n - 1) == 1] -- Reinhard Zumkeller, Jul 17 2014
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Maple
f:= proc(n) local k; for k from 1 do if isprime(n^k+n-1) then return k fi od end proc: map(f, [$2..112]); # Robert Israel, Apr 07 2025 -
Mathematica
lk[n_]:=Module[{k=1},While[!PrimeQ[n^k+n-1],k++];k]; Array[lk,100,2] (* Harvey P. Dale, Jun 29 2017 *) -
PARI
a(n) = {my(k=1); while(!isprime(n^k+n-1), k++); k;} \\ Michel Marcus, Nov 29 2013
Comments