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Search: id:A113520
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| A113520 |
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a(n) = largest nonprime nonnegative integer < n which is coprime to n. |
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+0
1
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| 0, 1, 1, 1, 4, 1, 6, 1, 8, 9, 10, 1, 12, 9, 14, 15, 16, 1, 18, 9, 20, 21, 22, 1, 24, 25, 26, 27, 28, 1, 30, 27, 32, 33, 34, 35, 36, 35, 38, 39, 40, 25, 42, 39, 44, 45, 46, 35, 48, 49, 50, 51, 52, 49, 54, 55, 56, 57, 58, 49, 60, 57, 62, 63, 64, 65, 66, 65, 68
(list; graph; listen)
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OFFSET
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1,5
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COMMENT
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a(1) = 0 because 0 is coprime with 1, for our purposes, and is < 1.
The numbers n with a(n) = 1 are given in A048597. - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Oct 16 2007
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EXAMPLE
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a(14) = 9 because 9 is the largest non-prime integer < 14 which is coprime to 14 (since the other non-prime integers > 9 and < 14 {10 and 12} aren't coprime with 14).
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MATHEMATICA
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a = {0}; For[n = 2, n < 70, n++, i = n - 1; While[PrimeQ[i] || GCD[n, i] > 1, i-- ]; AppendTo[a, i]]; a - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Oct 16 2007
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CROSSREFS
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Sequence in context: A100796 A005451 A135683 this_sequence A087652 A072195 A032310
Adjacent sequences: A113517 A113518 A113519 this_sequence A113521 A113522 A113523
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KEYWORD
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more,nonn
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AUTHOR
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Leroy Quet (qq-quet(AT)mindspring.com), Jan 12 2006
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EXTENSIONS
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More terms from Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Oct 16 2007
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