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

3, 2, 2, 2, 2, 8, 6, 2, 2, 8, 2, 4, 2, 6, 4, 12, 4, 9, 2, 3, 2, 31, 2, 11, 16, 9, 4, 2, 10, 3, 27, 4, 12, 36, 25, 3, 16, 24, 34, 3, 91, 85, 12, 105, 6, 8, 72, 6, 7, 25, 98, 3, 66, 103, 22, 32, 55, 4, 42, 6, 25, 20, 12, 4, 14, 303, 14, 115, 69, 46, 13, 3, 45, 4, 5, 68, 31, 31, 9, 8, 5, 4, 16

Offset: 2

Author

Artur Jasinski, Jan 19 2007

Keywords

• nonn

Links

• Harvey P. Dale, Table of n, a(n) for n = 2..500

Crossrefs

Cf. A126439.

Programs

Mathematica

a = {}; Do[k = 2; While[ ! PrimeQ[k^n - k - 1], k++ ]; AppendTo[a, k], {n, 2, 100}]; a (* Artur Jasinski *)
lnx[n_]:=Module[{x=1},While[!PrimeQ[x^n-x-1],x++];x]; Array[lnx,90,2] (* Harvey P. Dale, Jan 10 2017 *)

PARI

a(n)=k=1;while(!isprime(k^n-k-1),k++);k
vector(100,n,a(n+1)) \\ Derek Orr, Nov 26 2014