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A046901
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a(n) = a(n-1)-n if a(n-1)>n, else a(n) = a(n-1)+n.
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13
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1, 3, 6, 2, 7, 1, 8, 16, 7, 17, 6, 18, 5, 19, 4, 20, 3, 21, 2, 22, 1, 23, 46, 22, 47, 21, 48, 20, 49, 19, 50, 18, 51, 17, 52, 16, 53, 15, 54, 14, 55, 13, 56, 12, 57, 11, 58, 10, 59, 9, 60, 8, 61, 7, 62, 6, 63, 5, 64, 4, 65, 3, 66, 2, 67, 1, 68, 136, 67, 137
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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COMMENTS
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Variation (1) on Recaman's sequence A005132.
a(A134931(n-1)) = 1. - Reinhard Zumkeller, Jan 31 2013
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LINKS
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N. J. A. Sloane, First 10000 terms
Index entries for sequences related to Recaman's sequence
Nick Hobson, Python program for this sequence
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FORMULA
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This is a concatenation S_0, S_1, S_2, ... where S_i = [b_0, b_1, ..., b_{k-1}], k=5*3^i, with b_0 = 1, b_{2j} = k+j, b_{2j+1} = (k+1)/2-j. E.g. S_0 = [1, 3, 6, 2, 7].
For any m>=1, for k such that 5*3^k+3>12m, a((5*3^k+3-12*m)/6)= m. For example, for k>=1, a((5*3^k-9)/6) = 1. - Benoit Cloitre Oct 31, 2002
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MAPLE
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A046901 := proc(n) option remember; if n = 1 then 1 else if A046901(n-1)>n then A046901(n-1)-n else A046901(n-1)+n; fi; fi; end;
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MATHEMATICA
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a[1]=1; a[n_]:=a[n]=If[a[n-1]>n, a[n-1]-n, a[n-1]+n]; Table[a[i], {i, 70}] (* From Harvey P. Dale, Apr 01 2011 *)
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PROG
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(PARI) a(n)=if(n<2, 1, a(n-1)-if(sign(n-a(n-1))+1, -1, 1)*n)
(Haskell)
a046901 n = a046901_list !! (n-1)
a046901_list = f 1 2 where
f v w = y : f (v + 1) y where
y = if w > v then w - v else w + v
-- Reinhard Zumkeller, Jan 31 2013
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CROSSREFS
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Cf. A008344, A005132.
Cf. A076039, A076040, A076041, A076042, A057198.
Cf. A085059.
Sequence in context: A118453 A021969 A172372 * A169751 A105332 A186706
Adjacent sequences: A046898 A046899 A046900 * A046902 A046903 A046904
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KEYWORD
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easy,nonn,nice
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AUTHOR
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N. J. A. Sloane.
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STATUS
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approved
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