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 A057887 Number of 4-tuples of integers with GCD=1 and giving the lengths of sides of a nondegenerate quadrilateral with perimeter n. 2
 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; refs; listen; history; text; internal format)
 OFFSET 1,6 LINKS FORMULA Moebius transform of A057886. EXAMPLE 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. CROSSREFS Cf. A051493. Sequence in context: A211659 A301806 A066847 * A202116 A215914 A006049 Adjacent sequences:  A057884 A057885 A057886 * A057888 A057889 A057890 KEYWORD nonn AUTHOR John W. Layman, Sep 19 2000 STATUS approved

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Last modified August 13 02:09 EDT 2020. Contains 336441 sequences. (Running on oeis4.)