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Search: id:A137864
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| A137864 |
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a(n) = n^4-10n^3+35n^2-48n+23. |
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+0
1
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| 1, 3, 5, 7, 33, 131, 373, 855, 1697, 3043, 5061, 7943, 11905, 17187, 24053, 32791, 43713, 57155, 73477, 93063, 116321, 143683, 175605, 212567, 255073, 303651, 358853, 421255, 491457, 570083, 657781, 755223, 863105, 982147
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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This sequence appears at first to be the sequence of odd numbers but then rapidly becomes something different altogether. It is a good example of why more than a few terms are needed to check a hypothesis.
Useful for practising the method of finite differences
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REFERENCES
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A. Watson and J. Mason, Mathematics as a Constructive Activity, LEA London, 2005, p. 162.
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LINKS
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Author?, Method of Finite Differences.
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FORMULA
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O.g.f.: -x*(1-2*x+2*x^3+23*x^4)/(-1+x)^5 . - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Feb 19 2008
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EXAMPLE
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a(5) = 33 the first term that breaks with the odd number pattern.
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CROSSREFS
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Cf. A005408.
Sequence in context: A002396 A029508 A095714 this_sequence A069969 A067232 A106115
Adjacent sequences: A137861 A137862 A137863 this_sequence A137865 A137866 A137867
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KEYWORD
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easy,more,nonn
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AUTHOR
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Christopher Martin (christopher.j.martin(AT)gmail.com), Feb 17 2008
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Feb 19 2008
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