A090087 - OEIS

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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

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OFFSET

1,1

LINKS

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

FORMULA

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

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 *)

CROSSREFS

Cf. A007535, A090986, A090088, A090089.

Sequence in context: A100569 A244503 A152553 * A090085 A098650 A354689

Adjacent sequences: A090084 A090085 A090086 * A090088 A090089 A090090

KEYWORD

nonn

AUTHOR

Labos Elemer, Nov 25 2003

STATUS

approved