A070109 - OEIS

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A070109

Number of right integer triangles with perimeter n and relatively prime side lengths.

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,1`
	COMMENTS	`a(n)<=A024155(n); a(n)=A051493(n)-A070094(n)-A070102(n);` `right integer triangles have integer areas: see A070142, A051516.` `a(n) is nonzero iff n is in A024364.`
	LINKS	`Eric Weisstein's World of Mathematics, Right Triangle.` `Eric Weisstein's World of Mathematics, Pythagorean Triples.` `R. Zumkeller, Integer-sided triangles`
	FORMULA	`a(n)=A078926(n/2) if n is even; a(n)=0 if n is odd.`
	EXAMPLE	`For n=30 there are A005044(30) = 19 integer triangles; only one is right: 5+12+13=30, 5^2+12^2 = 13^2; therefore a(30) = 1.`
	CROSSREFS	`Cf. A070080, A070081, A070082, A051493, A070093, A070101, A070138, A070084, A070137.` `Sequence in context: A011727 A088918 A011726 * A107846 A179801 A065202` `Adjacent sequences: A070106 A070107 A070108 * A070110 A070111 A070112`
	KEYWORD	`nonn`
	AUTHOR	`Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), May 05 2002`

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Last modified February 17 16:49 EST 2012. Contains 206058 sequences.