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A176817
Nonprimes k such that 2^(k-1) == 4^(k-1) (mod k).
1
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
OFFSET
1,2
COMMENTS
All powers of two are present.
MATHEMATICA
fQ[n_] := !PrimeQ@ n && PowerMod[2, n - 1, n] == PowerMod[4, n - 1, n]; Select[ Range@ 10000, fQ]
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved