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Search: id:A070101
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| A070101 |
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Number of obtuse integer triangles with perimeter n. |
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+0
15
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| 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 2, 0, 2, 2, 3, 2, 3, 3, 5, 3, 7, 4, 8, 5, 9, 7, 10, 8, 11, 9, 14, 11, 16, 12, 18, 14, 19, 17, 21, 18, 23, 21, 27, 22, 30, 24, 32, 27, 34, 30, 37, 33, 40, 35, 44, 37, 47, 40, 50, 44, 53, 49, 56, 52, 60, 55, 64, 57, 68
(list; graph; listen)
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OFFSET
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1,11
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COMMENT
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An integer triangle [A070080(k)<=A070081(k)<=A070082(k)] is obtuse iff A070085(k)<0;
a(n) = A005044(n) - A070093(n) - A024155(n);
a(n) = A024156(n) + A070106(n).
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LINKS
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Eric Weisstein's World of Mathematics, Obtuse Triangle.
R. Zumkeller, Integer-sided triangles
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EXAMPLE
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For n=14 there are A005044(14)=4 integer triangles: [2,6,6], [3,5,6], [4,4,6] and [4,5,5]; two of them are obtuse, as 3^2+5^2<36=6^2 and 4^2+4^2<36=6^2, therefore a(14)=2.
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CROSSREFS
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Cf. A070102, A070103, A070127.
Sequence in context: A061199 A144741 A103615 this_sequence A022830 A035663 A117192
Adjacent sequences: A070098 A070099 A070100 this_sequence A070102 A070103 A070104
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KEYWORD
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nonn
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AUTHOR
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Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), May 05 2002
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