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Search: id:A112403
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| A112403 |
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G.f.: (1-16*x+28*x^2+56*x^3-140*x^4+56*x^5+28*x^6-16*x^7+x^8)/(x^2-x+1)^8. |
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+0
1
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| 1, -8, -72, -120, 330, 1584, 1716, -3432, -12870, -11440, 19448, 63648, 50388, -77520, -232560, -170544, 245157, 692208, 480700, -657800, -1776060, -1184040, 1560780, 4071600, 2629575, -3365856, -8544096, -5379616
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Sequence is interesting because the initial terms seem to have many small factors.
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FORMULA
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a(n) = 2 cos(pi (n+1)/3) binomial(n+7,7). Note that 2 cos(pi (n+1)/3) is always 1, -1, 2, or -2, so this formula explains the small factors. - Dean Hickerson (dean(AT)math.ucdavis.edu), Feb 06 2006
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CROSSREFS
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Sequence in context: A032554 A097255 A115693 this_sequence A043932 A064015 A044576
Adjacent sequences: A112400 A112401 A112402 this_sequence A112404 A112405 A112406
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KEYWORD
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sign
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AUTHOR
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Creighton Dement, Dec 06 2005
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