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A072530
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Number of primes p such that n divided by p leaves a prime remainder.
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7
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0, 0, 0, 0, 1, 0, 1, 2, 1, 1, 1, 2, 2, 2, 1, 3, 3, 3, 2, 3, 1, 3, 3, 5, 2, 4, 2, 4, 3, 4, 3, 4, 4, 3, 2, 6, 4, 5, 2, 6, 4, 6, 3, 6, 4, 5, 5, 7, 4, 6, 4, 5, 4, 8, 3, 5, 4, 7, 5, 9, 3, 7, 5, 8, 5, 7, 3, 8, 4, 8, 5, 10, 6, 7, 5, 8, 4, 9, 6, 9, 7, 8, 4, 10, 5, 7, 6, 8, 7, 12, 5, 8, 8, 8, 5, 12, 6, 10, 5, 10, 5
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,8
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COMMENTS
| Is there any n > 6 such that a(n) =0 ?
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EXAMPLE
| a(17) = 3: there are 3 primes viz. 3, 5 and 7 which leave prime remainders on dividing 17.
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MATHEMATICA
| Table[Count[PrimeQ[Table[Mod[w, Prime[j]], {j, 1, PrimePi[w]}]], True], {w, 1, 256}]
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CROSSREFS
| Cf. A072531.
Sequence in context: A087048 A109700 A087742 * A184341 A090455 A086288
Adjacent sequences: A072527 A072528 A072529 * A072531 A072532 A072533
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KEYWORD
| nonn
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Aug 01 2002
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EXTENSIONS
| More terms from Labos E. (labos(AT)ana.sote.hu), Aug 02 2002
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