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A128859
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Let p be the n-th odd prime; a(n) is the number of primitive roots of p which are <= (p-1)/2.
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2
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0, 1, 1, 1, 2, 4, 2, 4, 6, 4, 6, 8, 6, 9, 12, 10, 8, 10, 9, 12, 10, 16, 20, 16, 20, 13, 22, 18, 24, 17, 18, 32, 18, 36, 16, 24, 26, 36, 42, 37, 24, 29, 32, 42, 23, 16, 38, 49, 36, 56, 44, 32, 44, 64, 59, 66, 33, 44, 48, 40, 72, 48, 55, 48, 78, 35, 48, 79, 56, 80, 80, 60, 60, 55
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OFFSET
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1,5
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REFERENCES
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Roger Osborn, Tables of All Primitive Roots of Odd Primes Less Than 1000, Univ. Texas Press, Austin, TX, 1961, pp. 69-70.
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LINKS
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MATHEMATICA
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a[n_] := Count[PrimitiveRootList[(p = Prime[n+1])], _?(# <= (p-1)/2 &)]; Array[a, 100]
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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