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Search: id:A057887
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| A057887 |
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Number of 4-tuples of integers with GCD=1 and giving the lengths of sides of a nondegenerate quadrilateral with perimeter n. |
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2
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| 0, 0, 0, 1, 1, 2, 3, 4, 7, 8, 13, 13, 22, 22, 33, 33, 50, 45, 70, 65, 92, 87, 125, 111, 160, 145, 196, 184, 252, 215, 308, 278, 359, 330, 440, 385, 525, 464, 593, 546, 715, 606, 825, 735, 905, 832, 1078, 926, 1219, 1065, 1328, 1223, 1547, 1310, 1715, 1529, 1855
(list; graph; listen)
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OFFSET
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1,6
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FORMULA
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Moebius transform of A057886.
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EXAMPLE
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There are five quadrilaterals with perimeter 8, with sides (1,1,3,3), (1,2,2,3), (1,2,3,2), (1,3,1,3) and (2,2,2,2). (2,2,2,2) is omitted since it has GCD=2, so a(8)=4.
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CROSSREFS
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Cf. A051493.
Sequence in context: A015840 A051213 A066847 this_sequence A006049 A084541 A113050
Adjacent sequences: A057884 A057885 A057886 this_sequence A057888 A057889 A057890
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KEYWORD
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nonn
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AUTHOR
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John W. Layman (layman(AT)math.vt.edu), Sep 19 2000
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