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A337829 Odd integers k such that 5^((k-1)/2) + 1 == 0 (mod k*(k-1)/2). 1
3, 7, 43, 53, 127, 163, 487, 677, 883, 2647, 8527, 8803, 14407, 18523, 26407, 32887, 35323, 39367, 71443, 105967, 184087, 184843, 230203, 265483, 319327, 388963, 425083, 543607, 554527, 651043, 688087, 690607, 698923, 796447, 887923, 924043, 1001323 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The first 564 terms are prime.

LINKS

Chai Wah Wu, Table of n, a(n) for n = 1..564

MATHEMATICA

Select[Range[3, 10^6, 2], PowerMod[5, (# - 1)/2, (t = #*(# - 1)/2)] == t - 1 &] (* Amiram Eldar, Sep 24 2020 *)

CROSSREFS

Cf. A337818.

Sequence in context: A217759 A160615 A106965 * A257366 A141304 A213893

Adjacent sequences:  A337826 A337827 A337828 * A337830 A337831 A337832

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Sep 24 2020

STATUS

approved

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Last modified October 23 14:42 EDT 2021. Contains 348214 sequences. (Running on oeis4.)