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A118906
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a(0) = 1; a(n) = |a(n-1) - n| if n is not one of the earlier terms of the sequence, otherwise a(n) = a(n-1) + n.
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1
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1, 2, 4, 1, 5, 10, 4, 3, 5, 4, 14, 3, 9, 4, 18, 3, 13, 4, 22, 3, 17, 4, 26, 3, 21, 4, 30, 3, 25, 4, 34, 3, 29, 4, 38, 3, 33, 4, 42, 3, 37, 4, 46, 3, 41, 4, 50, 3, 45, 4, 54, 3, 49, 4, 58, 3, 53, 4, 62, 3, 57, 4, 66, 3, 61, 4, 70, 3, 65, 4, 74, 3, 69, 4, 78, 3, 73, 4, 82, 3, 77, 4, 86, 3, 81, 4
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OFFSET
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0,2
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LINKS
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Table of n, a(n) for n=0..85.
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MAPLE
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a[0]:=1: S:={1}: for n from 1 to 100 do if member(n, S)=false then a[n]:=abs(a[n-1]-n): S:=S union {a[n]} else a[n]:=a[n-1]+n: S:=S union {a[n]} fi od: seq(a[n], n=0..100); - Emeric Deutsch, May 07 2006
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MATHEMATICA
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f[s_] := Block[{n, }, n = Length[s]; Return[Append[s, Abs[Last[s] + If[MemberQ[s, n], +n, -n]]]]; ]; Nest[f, {1}, 100] (*Chandler*)
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CROSSREFS
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Cf. A118907, A005132.
Sequence in context: A059573 A201283 A080427 * A085059 A181336 A124037
Adjacent sequences: A118903 A118904 A118905 * A118907 A118908 A118909
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KEYWORD
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easy,nonn
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AUTHOR
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Leroy Quet May 05 2006
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EXTENSIONS
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Extended by Ray Chandler and Emeric Deutsch, May 06 2006
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STATUS
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approved
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