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Search: id:A072301
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| A072301 |
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Number of positive integers not exceeding n that are relatively prime to sigma(n). |
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+0
1
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| 1, 2, 2, 4, 2, 2, 4, 5, 9, 3, 4, 5, 6, 5, 5, 16, 6, 11, 8, 6, 11, 7, 8, 7, 25, 8, 11, 12, 8, 10, 16, 19, 11, 11, 12, 29, 18, 10, 17, 10, 12, 14, 20, 13, 14, 15, 16, 23, 31, 33, 17, 22, 18, 15, 19, 15, 23, 15, 16, 17, 30, 21, 30, 64, 19, 22, 32, 20, 23, 23, 24, 35, 36, 24, 37, 26, 26
(list; graph; listen)
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OFFSET
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1,2
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EXAMPLE
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Among the positive integers not exceeding 12, the five numbers 1,3,5,9,11 are relatively prime to sigma(12)=28. Hence a(12)=5.
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MATHEMATICA
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r = {}; Do[ s = DivisorSigma[1, n]; j = 0; For[i = 1, i <= n, i++, If[GCD[s, i] == 1, j++ ]]; r = Append[r, j], {n, 1, 10^2}]; r
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CROSSREFS
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Sequence in context: A087692 A093621 A143230 this_sequence A127171 A118232 A115070
Adjacent sequences: A072298 A072299 A072300 this_sequence A072302 A072303 A072304
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KEYWORD
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base,nonn
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AUTHOR
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Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Jul 14 2002
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