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A055687 Numbers n such that 4^n == -1 (mod n-1). 0
2, 18, 4098, 7362, 85074, 658530, 3999138, 72281282, 285143058, 628944690, 854112114, 1423081170, 2561019282, 3111576930, 4298117634, 5921265042, 14224884930, 21336998130, 34317377234, 50723421714, 63797137890, 144269032050, 163834314354, 187397322210, 212565453282, 231286579794, 232992827298, 266198715090, 314834584482, 348160787730, 580045717650, 706501722498 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..32.

MATHEMATICA

Do[If[PowerMod[4, n, n-1]==n-2, Print[n]], {n, 2, 10^8}]

CROSSREFS

Sequence in context: A206847 A259654 A060598 * A006262 A003043 A059783

Adjacent sequences:  A055684 A055685 A055686 * A055688 A055689 A055690

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Jun 09 2000

EXTENSIONS

Terms a(9) onward from Max Alekseyev, Oct 12 2012

STATUS

approved

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Last modified April 8 05:55 EDT 2020. Contains 333312 sequences. (Running on oeis4.)