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Search: id:A020653
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| A020653 |
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Denominators in canonical bijection from positive integers to positive rationals. |
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+0
15
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| 1, 2, 1, 3, 1, 4, 3, 2, 1, 5, 1, 6, 5, 4, 3, 2, 1, 7, 5, 3, 1, 8, 7, 5, 4, 2, 1, 9, 7, 3, 1, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 11, 7, 5, 1, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 13, 11, 9, 5, 3, 1, 14, 13, 11, 8, 7, 4, 2, 1, 15, 13, 11, 9, 7, 5, 3, 1, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 17
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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Richard Courant and Herbert Robbins. What Is Mathematics?, Oxford, 1941, pp. 79-80.
H. Lauwerier, Fractals, Princeton Univ. Press, p. 23.
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LINKS
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David Wasserman, Table of n, a(n) for n = 1..100000
Index entries for "core" sequences
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MAPLE
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with (numtheory): A020653 := proc (n) local sum, j, k; sum := 0: k := 2: while (sum < n) do: sum := sum + phi(k): k := k + 1: od: sum := sum - phi(k-1): j := 1; while sum < n do: if gcd(j, k-1) = 1 then sum := sum + 1: fi: j := j+1: od: RETURN (k-j): end: # from UlrSchimke(AT)aol.com, Nov 06, 2001
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CROSSREFS
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Cf. A020652.
Sequence in context: A079786 A032451 A088445 this_sequence A094522 A118487 A091420
Adjacent sequences: A020650 A020651 A020652 this_sequence A020654 A020655 A020656
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KEYWORD
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nonn,frac,core,nice
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AUTHOR
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David W. Wilson (davidwwilson(AT)comcast.net)
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