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A160357
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Sign of first differences of Recamán's sequence A005132.
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10
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1, 1, 1, 1, -1, 1, 1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, 1, 1, -1, 1, -1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, 1, 1, -1, 1, -1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, 1, 1, -1, 1, -1
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OFFSET
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0,1
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LINKS
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T. D. Noe, Table of n, a(n) for n = 0..10000
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FORMULA
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a(n) = sign(A005132(n)-A005132(n-1)) = sign(A160356(n)) = (-1)^A160351(n) = -(-1)^A076213(n-1).
a(n) = (A005132(n)-A005132(n-1))/n. - N. J. A. Sloane, Jul 15 2011
A160357 = chi_A057165 - chi_A057166, where chi_A denotes the characteristic function of (the set of values of) A.
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MAPLE
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A160357 := proc(n)
sign( A005132(n)-A005132(n-1)) ;
end proc: # R. J. Mathar, Apr 01 2012
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MATHEMATICA
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f[s_List] := Module[{a = s[[-1]], n = Length[s]}, Append[s, If[a > n && FreeQ[s, a - n], a - n, a + n]]];
Nest[f, {0}, 100] // Differences // Sign (* Jean-François Alcover, Apr 19 2020, using Robert G. Wilson v's code for A005132 *)
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CROSSREFS
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Cf. A005132, A119632.
Sequence in context: A212157 A131554 A153881 * A186039 A332433 A057077
Adjacent sequences: A160354 A160355 A160356 * A160358 A160359 A160360
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KEYWORD
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sign
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AUTHOR
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M. F. Hasler, Jun 03 2009
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EXTENSIONS
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a(0)=1 added by N. J. A. Sloane, May 01 2020
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STATUS
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approved
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