A068563 Numbers n such that 2^n == 4^n (mod n).

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

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