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A078928
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Smallest p for which there are exactly n primitive Pythagorean triangles with perimeter p; i.e., smallest p such that A070109(p) = n.
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2
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12, 1716, 14280, 317460, 1542684, 6240360, 19399380, 63303240, 239168580, 397687290, 458948490, 813632820, 562582020, 2824441620, 3346393050, 6915878970, 6469693230, 8720021310, 9146807670, 8254436190, 23065862820, 25859373540, 202536455550
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OFFSET
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1,1
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COMMENTS
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A Pythagorean triangle is a right triangle whose edge lengths are all integers; such a triangle is 'primitive' if the lengths are relatively prime.
Least perimeter common to exactly n primitive Pythagorean triangles. - Lekraj Beedassy, May 14 2004
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LINKS
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EXAMPLE
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a(2)=1716; the primitive Pythagorean triangles with edge lengths (364, 627, 725) and (195, 748, 773) both have perimeter 1716.
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MATHEMATICA
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oddpart[n_] := If[OddQ[n], n, oddpart[n/2]]; ct[p_] := Length[Select[Divisors[oddpart[p/2]], p/2<#^2<p&&GCD[ #, p/2/# ]==1&]]; a[n_] := For[per=2, True, per+=2, If[ct[per]==n, Return[per]]]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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