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A055688
Numbers k such that 5^k == -1 (mod k-1).
3
2, 3, 7, 14, 15, 175, 855, 2695, 78127, 103974, 106695, 121975, 420210, 487375, 1299375, 2174655, 3895095, 4151455, 5842215, 5951130, 6508335, 10637055, 20117895, 24482958, 31999695, 32282054, 32620203, 32872455, 34258455
OFFSET
1,1
LINKS
MATHEMATICA
Do[If[PowerMod[5, n, n-1]==n-2, Print[n]], {n, 2, 10^8}]
Select[Range[2, 35*10^6], PowerMod[5, #, #-1]==#-2&] (* Harvey P. Dale, Aug 13 2024 *)
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Jun 09 2000
EXTENSIONS
a(22) corrected by Amiram Eldar, Jul 23 2021
STATUS
approved