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Search: id:A007527
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| A007527 |
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Numbers that are not the sum of 4 hexagonal numbers.
(Formerly M3793)
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+0
4
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| 5, 10, 11, 20, 25, 26, 38, 39, 54, 65, 70, 114, 130
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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The sequence is complete. "In 1830, Legendre (1979) proved that every number larger than 1791 is a sum of four hexagonal numbers". See http://mathworld.wolfram.com/HexagonalNumber.html and reference : A.-M. Legendre, Theorie des nombres, 4th ed., 2 vols. Paris: A. Blanchard, 1979. It is easy to check all numbers <= 1791 by computer. - Olivier Pirson (olivier_pirson_opi(AT)yahoo.fr), Sep 14 2007
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
R. K. Guy, Every number is expressible as the sum of how many polygonal numbers?, Amer. Math. Monthly 101 (1994), 169-172.
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LINKS
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Eric Weisstein's World of Mathematics, Hexagonal Number
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CROSSREFS
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Sequence in context: A136822 A120513 A004757 this_sequence A033894 A033649 A050680
Adjacent sequences: A007524 A007525 A007526 this_sequence A007528 A007529 A007530
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KEYWORD
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fini,nonn,full
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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