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 A253803 a(n) gives one fourth of the even leg of one of the two Pythagorean triangles with hypotenuse A080109(n) = A002144(n)^2. The odd leg is given in A253802(n). 3
 6, 39, 60, 210, 210, 410, 630, 915, 1320, 1780, 2340, 990, 2730, 3164, 4620, 5215, 5610, 4290, 8145, 8106, 2730, 6630, 12116, 12540, 4080, 17485, 17451, 18480, 9690, 24414 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS See A253802 for comments and the Dickson reference. REFERENCES L. E. Dickson, History of the Theory of Numbers, Carnegie Institution, Publ. No. 256, Vol. II, Washington D.C., 1920, p. 227. LINKS FORMULA a(n) = sqrt(A080109(n)^2 - A253802(n)^2)/4, n >= 1. EXAMPLE n = 7: A080175(7) = 7890481 = 53^4 = 2809^2; A002144(7)^4 = A253802(7)^2 + (4*a(7))^2 = 1241^2 + (4*630)^2. The other Pythagorean triangle with hypotenuse 53^2 = 2809 has odd leg A253804(7) = 2385 and even leg 4*A253305(7) = 4*371 = 1484: 53^4 = 2385^2 + (4*371)^2. CROSSREFS Cf. A002144, A080109, A253802, A253804, A253805. Sequence in context: A241258 A061423 A080298 * A058897 A058985 A116951 Adjacent sequences:  A253800 A253801 A253802 * A253804 A253805 A253806 KEYWORD nonn,easy AUTHOR Wolfdieter Lang, Jan 14 2015 STATUS approved

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Last modified November 26 07:25 EST 2020. Contains 338632 sequences. (Running on oeis4.)