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A111305
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Composite numbers n such that a^(n-1) = 1 mod n only when a = 1 mod n.
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0
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4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 54, 56, 58, 60, 62, 64, 68, 72, 74, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 104, 106, 108, 110, 114, 116, 118, 120, 122, 126, 128, 132, 134, 136, 138, 140, 142, 144
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| These unCarmichael numbers fail the Fermat primality test as often as possible.
All such numbers are even: for odd n, (-1)^(n-1) = 1.
The even numbers not in this sequence are 2 and A039772.
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EXAMPLE
| 10 is there because 3^9 = 3, 7^9 = 7, 9^9 = 9 mod 10.
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CROSSREFS
| Cf. A002997, A039772.
Sequence in context: A163300 A193175 A093161 * A175246 A134928 A141109
Adjacent sequences: A111302 A111303 A111304 * A111306 A111307 A111308
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KEYWORD
| nonn
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AUTHOR
| Karsten Meyer (arbol01(AT)gmx.de), Nov 02 2005
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EXTENSIONS
| Edited by Don Reble (djr(AT)nk.ca), May 16 2006
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