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Search: id:A020652
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| A020652 |
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Numerators in canonical bijection from positive integers to positive rationals. |
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+0
12
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| 1, 1, 2, 1, 3, 1, 2, 3, 4, 1, 5, 1, 2, 3, 4, 5, 6, 1, 3, 5, 7, 1, 2, 4, 5, 7, 8, 1, 3, 7, 9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 1, 5, 7, 11, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 1, 3, 5, 9, 11, 13, 1, 2, 4, 7, 8, 11, 13, 14, 1, 3, 5, 7, 9, 11, 13, 15, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 1, 5
(list; graph; listen)
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OFFSET
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1,3
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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 sequences related to Stern's sequences
Index entries for "core" sequences
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EXAMPLE
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..., 1/8, 2/7, 4/5, 5/4, 7/2, 8/1, ...
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MAPLE
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with (numtheory): A020652 := 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 (j-1): end: # from UlrSchimke(AT)aol.com, Nov 06, 2001
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CROSSREFS
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Essentially the same as A038566, which is the main entry for this sequence.
Cf. A020653, A038567-A038569.
A054424 gives mapping to Stern-Brocot tree.
Adjacent sequences: A020649 A020650 A020651 this_sequence A020653 A020654 A020655
Sequence in context: A132589 A054843 A038566 this_sequence A096107 A128487 A056609
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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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