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Search: id:A063867
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| A063867 |
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Number of solutions to +- 1 +- 2 +- 3 +- ... +- n = 0 or +- 1. |
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+0
8
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| 1, 2, 2, 2, 2, 6, 10, 8, 14, 46, 80, 70, 124, 442, 794, 722, 1314, 4820, 8882, 8220, 15272, 56920, 106444, 99820, 187692, 707486, 1336546, 1265204, 2399784, 9119656, 17358560, 16547220, 31592878, 120801376, 231266520, 221653776, 425363952
(list; graph; listen)
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OFFSET
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0,2
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REFERENCES
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Suggested by J. H. Conway (conway(AT)math.princeton.edu), Aug 27, 2001.
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LINKS
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T. D. Noe, Table of n, a(n) for n=0..100
S. R. Finch, Signum equations and extremal coefficients.
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MATHEMATICA
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f[n_, s_] := f[n, s]=Which[n==0, If[s==0, 1, 0], Abs[s]>(n*(n+1))/2, 0, True, f[ n-1, s-n]+f[n-1, s+n]]; a[n_] := f[n, 0]+2f[n, 1]
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CROSSREFS
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Cf. A025591, A063865, A063866.
Sequence in context: A139554 A116564 A078014 this_sequence A024723 A035470 A061292
Adjacent sequences: A063864 A063865 A063866 this_sequence A063868 A063869 A063870
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KEYWORD
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nonn,easy,nice
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Aug 27 2001
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EXTENSIONS
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More terms from Dean Hickerson and Vladeta Jovovic (vladeta(AT)eunet.rs), Aug 28, 2001
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