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Search: id:A113963
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| A113963 |
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a(1)=1; for n>1, a(n) is the smallest positive integer not occurring earlier in the sequence where |a(n)-a(n-1)| does not divide (a(n)+a(n-1)). |
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4
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| 1, 4, 7, 2, 5, 8, 3, 10, 13, 6, 11, 14, 9, 16, 19, 12, 17, 20, 23, 15, 22, 25, 18, 26, 21, 29, 24, 31, 27, 32, 35, 38, 28, 33, 37, 30, 39, 34, 40, 43, 36, 41, 44, 47, 42, 50, 53, 45, 49, 46, 51, 55, 48, 57, 52, 58, 61, 54, 59, 56, 62, 65, 68, 63, 67, 60, 69, 64, 70, 73, 66, 71
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Sequence is a permutation of the positive integers.
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EXAMPLE
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Among those positive integers not among the first 4 integers of the sequence, a(5) = 5 is the lowest such that |a(5)-a(4)| = |5-2| = 3 does not divide (a(5)+a(4)) = 5+2 = 7. 3, for example, is not among the first 4 terms of the sequence, but |3-2| = 1 does indeed divide (3+2). So a(5) is not 3, but is instead 5.
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MATHEMATICA
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f[l_] := Block[{k=1, m}, m = Last[l]; While[MemberQ[l, k] || Mod[m + k, Abs[k - m]] == 0, k++ ]; Return[Append[l, k]]; ]; Nest[f, {1}, 100] (*Chandler*)
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CROSSREFS
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Cf. A113964, A113965, A113966.
Sequence in context: A011351 A132026 A130882 this_sequence A071932 A139348 A021683
Adjacent sequences: A113960 A113961 A113962 this_sequence A113964 A113965 A113966
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet (qq-quet(AT)mindspring.com), Nov 10 2005
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EXTENSIONS
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Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Nov 13 2005
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