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 A089059 Numbers x such that xy/(x+y) is an integer and the hypotenuse of the right triangle with legs x and y is an integer. 0
 21, 42, 63, 84, 85, 105, 126, 147, 168, 170, 184, 189, 210, 217, 231, 252, 255, 273, 294, 315, 336, 340, 357, 368, 378, 399, 420, 425, 434, 441, 441, 462, 483 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS These numbers are almost always divisible by 7. 85 in the example is an exception and so is 184. LINKS EXAMPLE x=85,y=204, 85^2+204^2 = 221^2 PROG (PARI) xydivxpy2(n) = { for(x=1, n, for(y=x, n, h=x*y/(x+y); if(h==floor(h), z = sqrt (x^2+y^2); if(z==floor(z), print1(x", ") ) ) ) ) } CROSSREFS Sequence in context: A040420 A192130 A037978 * A114384 A008603 A235497 Adjacent sequences:  A089056 A089057 A089058 * A089060 A089061 A089062 KEYWORD nonn AUTHOR Cino Hilliard, Dec 02 2003, corrected Nov 23 2006 STATUS approved

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