A090087 Smallest odd pseudoprimes to base n, not necessarily exceeding n. Compare with A007535 and A090086.

9, 341, 91, 15, 217, 35, 25, 9, 91, 9, 15, 65, 21, 15, 341, 15, 9, 25, 9, 21, 55, 21, 33, 25, 39, 9, 65, 9, 15, 49, 15, 25, 85, 15, 9, 35, 9, 39, 95, 39, 15, 205, 21, 9, 133, 9, 65, 49, 15, 21, 25, 51, 9, 55, 9, 15, 25, 57, 15, 341, 15, 9, 341, 9, 33, 65, 33, 25, 35, 69, 9, 85, 9, 15

Offset: 1

Author

Labos Elemer, Nov 25 2003

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A007535, A090986, A090088, A090089.

Programs

Mathematica

a[n_] := Module[{k = 1}, While[GCD[n, k] > 1 || PrimeQ[k] || PowerMod[n, k - 1, k] != 1, k += 2]; k]; Array[a, 100] (* Amiram Eldar, Nov 11 2019 *)

Formula

a(n)=Min{x=odd number; Mod[ -1+n^(x-1), x]=0}