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Search: id:A086686
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| A086686 |
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Number of 1<=i<n such that i*n-1 is prime. |
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+0
1
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| 0, 0, 2, 3, 1, 5, 2, 4, 3, 5, 2, 8, 1, 7, 5, 7, 3, 10, 4, 9, 6, 10, 3, 13, 6, 8, 7, 11, 5, 19, 6, 9, 7, 9, 6, 18, 5, 13, 9, 16, 5, 22, 7, 16, 13, 12, 9, 19, 7, 16, 11, 15, 8, 21, 12, 16, 14, 14, 6, 33
(list; graph; listen)
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OFFSET
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1,3
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EXAMPLE
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For n=10, i=2,3,6,8,9 give primes, so a(10)=5
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PROGRAM
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(PARI) nphi(n)=local(c); c=0; for (i=1, n-1, if (isprime(i*n-1), c++)); c for(i=1, 60, print1(", "nphi(i)))
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CROSSREFS
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Sequence in context: A095195 A076791 A075014 this_sequence A021816 A055023 A126773
Adjacent sequences: A086683 A086684 A086685 this_sequence A086687 A086688 A086689
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KEYWORD
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nonn
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AUTHOR
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Jon Perry (perry(AT)globalnet.co.uk), Jul 28 2003
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