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 A094807 Numbers n such that primitive solutions for 1/n^2 = 1/x^2 + 1/y^2 exist. 1
 12, 60, 120, 168, 360, 420, 660, 1008, 1092, 1260, 1680, 1848, 1980, 2448, 2640, 2772, 3120, 3420, 3432, 4620, 4680, 5148, 5460, 6072, 7140, 7800, 8160, 8580, 9240, 9828, 10032, 11220, 11628, 12180, 13260, 14280, 14880, 15708, 15912, 15960, 17940 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Numbers n that are the product of two legs of a primitive Pythagorean triangle, that is, n = 2xy(x^2-y^2) where x and y are two relatively prime positive integers of different parity and x is greater than y. Numbers n which are the length of the altitude on the hypotenuse of a Pythagorean triangle and the smallest in its similarity class. REFERENCES E. Bahier, Recherche Methodique et Proprietes des Triangles Rectangles en Nombres Entiers, Hermann, Paris, 1916. p. 68. LINKS FORMULA Equals 2*A024365(n). EXAMPLE 12 is in the sequence because we have 1/12^2 = 1/15^2 + 1/20^2 and gcd(12,15,20)=1. CROSSREFS Sequence in context: A097191 A338159 A273691 * A120644 A099829 A099830 Adjacent sequences:  A094804 A094805 A094806 * A094808 A094809 A094810 KEYWORD nonn AUTHOR Lekraj Beedassy, Jun 11 2004 EXTENSIONS Comments provided by Michael Somos, Oct 01 2004 STATUS approved

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Last modified April 18 19:07 EDT 2021. Contains 343089 sequences. (Running on oeis4.)