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A009005
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All natural numbers except 1, 2 and 4.
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3
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3, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Short legs of Pythagorean triangles.
Also the natural numbers n such that there is an open knight's tour of the 4 X n chessboard. - Additional comments from Sharon Sela (sharonsela(AT)hotmail.com), Jan 02 2002
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LINKS
| IBM Ponder This, 2001
Index to sequences with linear recurrences with constant coefficients, signature (2,-1).
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FORMULA
| O.g.f.: x(3-x-x^2)/(1-x)^2. a(n)=A009056(n), n>1. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 26 2008
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PROG
| (PARI) a(n)=n+4-(n==1) \\ Charles R Greathouse IV, Sep 02 2011
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CROSSREFS
| Sequence in context: A196112 A009004 A005527 * A138884 A008521 A039231
Adjacent sequences: A009002 A009003 A009004 * A009006 A009007 A009008
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KEYWORD
| nonn,easy
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AUTHOR
| David W. Wilson (davidwwilson(AT)comcast.net)
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EXTENSIONS
| Additional comments from Sharon Sela (sharonsela(AT)hotmail.com), Jan 02 2002
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