A176817 - OEIS

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A176817

Nonprimes k such that 2^(k-1) == 4^(k-1) (mod k).

1, 4, 8, 16, 28, 32, 64, 112, 128, 256, 341, 448, 496, 512, 561, 645, 1016, 1024, 1105, 1288, 1387, 1729, 1792, 1905, 2044, 2047, 2048, 2416, 2465, 2701, 2821, 3277, 4033, 4096, 4369, 4371, 4672, 4681, 4984, 5461, 6601, 7168, 7936, 7957, 8128, 8192, 8321, 8481, 8911

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OFFSET

1,2

COMMENTS

All powers of two are present.

LINKS

Table of n, a(n) for n=1..49.

MATHEMATICA

fQ[n_] := !PrimeQ@ n && PowerMod[2, n - 1, n] == PowerMod[4, n - 1, n]; Select[ Range@ 10000, fQ]

CROSSREFS

Cf. A062173, A062175, A176176.

Sequence in context: A273029 A273080 A020193 * A050856 A271649 A128441

Adjacent sequences: A176814 A176815 A176816 * A176818 A176819 A176820

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, Dec 07 2010

STATUS

approved