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A068563 Numbers n such that 2^n == 4^n (mod n). 8
1, 2, 4, 6, 8, 12, 16, 18, 20, 24, 32, 36, 40, 42, 48, 54, 60, 64, 72, 80, 84, 96, 100, 108, 120, 126, 128, 136, 144, 156, 160, 162, 168, 180, 192, 200, 216, 220, 240, 252, 256, 272, 288, 294, 300, 312, 320, 324, 336, 342, 360, 378, 384, 400, 408, 420, 432, 440 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

If k is in the sequence then 2k is also in the sequence, but the converse is not true.

Contains A124240 as a subsequence. Their difference is given by A124241. - T. D. Noe, May 30 2003

Also, integers n such that A007733(n) divides n. Also, integers n such that for every odd prime divisor p of n, A007733(p) = A002326((p-1)/2) divides n. Also, integers n such that A000265(n) divides 2^n-1. - Max Alekseyev, Aug 25 2013

LINKS

T. D. Noe, Table of n, a(n) for n = 1..1000

Eric Weisstein's World of Mathematics, Carmichael Function

MATHEMATICA

Select[Range[500], PowerMod[2, #, # ] == PowerMod[4, #, # ] & ]

CROSSREFS

Cf. A002322.

Sequence in context: A258118 A177807 A305726 * A124240 A320580 A325763

Adjacent sequences:  A068560 A068561 A068562 * A068564 A068565 A068566

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre, Mar 25 2002

EXTENSIONS

Comment and Mathematica program corrected by T. D. Noe, Oct 17 2008

STATUS

approved

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Last modified October 18 12:18 EDT 2019. Contains 328160 sequences. (Running on oeis4.)