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Search: id:A138291
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| A138291 |
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Number of primes of the form prime(n)+g, where g is a primitive root of prime(n). |
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+0
1
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| 1, 1, 1, 0, 3, 1, 3, 1, 2, 4, 2, 2, 4, 3, 2, 7, 10, 3, 3, 3, 4, 6, 10, 7, 6, 11, 7, 12, 7, 9, 6, 10, 14, 10, 17, 10, 10, 12, 11, 13, 22, 7, 9, 11, 16, 10, 5, 13, 23, 8, 23, 12, 9, 23, 26, 22, 25, 13, 12, 14, 13, 19, 12, 18, 14, 32, 17, 18, 30, 22, 32, 21, 20, 14, 17, 28, 30, 19, 19, 21
(list; graph; listen)
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OFFSET
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1,5
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COMMENT
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It appears that only a(4), corresponding to the prime 7, is zero.
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..2000
Eric Weisstein, MathWorld: Primitive Root
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EXAMPLE
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a(5)=3 because the primitive roots of 11 are 2, 6, 7 and 8. Adding these numbers to 11 produce three primes: 13, 17 and 19.
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MATHEMATICA
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Join[{1}, Table[p=Prime[n]; g=Select[Range[2, p-1], MultiplicativeOrder[ #, p]==p-1&]; Length[Select[p+g, PrimeQ]], {n, 2, 2000}]]
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CROSSREFS
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Cf. A047934, A060749 (triangle of primitive roots of primes).
Sequence in context: A003636 A078929 A030728 this_sequence A062174 A154754 A102368
Adjacent sequences: A138288 A138289 A138290 this_sequence A138292 A138293 A138294
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KEYWORD
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nonn
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AUTHOR
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T. D. Noe (noe(AT)sspectra.com), Mar 12 2008
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