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A176176 Numbers n such that (2^(n-1) mod n)=(4^(n-1) mod n). 2
1, 2, 3, 4, 5, 7, 8, 11, 13, 16, 17, 19, 23, 28, 29, 31, 32, 37, 41, 43, 47, 53, 59, 61, 64, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 112, 113, 127, 128, 131, 137, 139, 149, 151, 157, 163, 167 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Numbers n such that A062173(n)=A062175(n).

Question: is the sequence (Powers of 2) UNION (odd primes), the union of A000079 and A005408?

The answer to the question is No: 2^(28-1) mod 28 = 4^(28-1) mod 28 = 8.  Also, any base-2 Fermat pseudoprime (A001567) is a member of this sequence. - D. S. McNeil, Dec 07 2010

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..10000

MATHEMATICA

Select[Range[200], PowerMod[2, #-1, #]==PowerMod[4, #-1, #]&] (* Harvey P. Dale, Nov 10 2011 *)

CROSSREFS

Cf. A000079, A005408, A062173.

Sequence in context: A081730 A162408 A162721 * A174090 A280083 A020902

Adjacent sequences:  A176173 A176174 A176175 * A176177 A176178 A176179

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, Dec 07 2010

EXTENSIONS

Extended by D. S. McNeil, Dec 07 2010

STATUS

approved

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Last modified January 19 21:47 EST 2020. Contains 331066 sequences. (Running on oeis4.)