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Search: id:A079327
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| A079327 |
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Smallest nonnegative integer x such that b^(n-1) == b^x (mod n) for all b such that 0<b<n. |
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+0
1
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| 0, 0, 0, 3, 0, 1, 0, 3, 2, 1, 0, 3, 0, 1, 2, 7, 0, 5, 0, 3, 2, 1, 0, 3, 4, 1, 8, 3, 0, 1, 0, 7, 2, 1, 10, 5, 0, 1, 2, 3, 0, 5, 0, 3, 8, 1, 0, 7, 6, 9, 2, 3, 0, 17, 14, 7, 2, 1, 0, 3, 0, 1, 2, 15, 4, 5, 0, 3, 2, 9, 0, 5, 0, 1, 14, 3, 16, 5, 0, 7, 26, 1, 0, 5, 4, 1, 2, 7, 0, 5, 6, 3, 2, 1, 22, 7, 0, 13, 8
(list; graph; listen)
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OFFSET
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1,4
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COMMENT
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a(n)=0 iff n=1 or n is prime.
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EXAMPLE
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a(5) = 0, since for all 1<=b<5 it is true that b^0 mod 5 == b^(5-1) mod 5 (hence 5 is prime). a(9) = 2, since for all 1<=b<9 it is true that b^2 mod 9 == b^(9-1) mod 9 (hence 9 is composite).
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MATHEMATICA
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a[n_] := For[x=0, True, x++, If[Mod[Range[n-1]^(n-1), n]==Mod[Range[n-1]^x, n], Return[x]]]
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CROSSREFS
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Adjacent sequences: A079324 A079325 A079326 this_sequence A079328 A079329 A079330
Sequence in context: A109718 A053385 A035640 this_sequence A123878 A108197 A049769
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KEYWORD
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easy,nonn
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AUTHOR
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Gottfried Helms (helms(AT)uni-kassel.de), Feb 13 2003
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EXTENSIONS
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Edited by Dean Hickerson (dean(AT)math.ucdavis.edu), Feb 15 2003
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