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%I #3 Oct 01 2013 17:57:46
%S 2,3,4,4,5,6,6,6,7,8,8,8,9,9,10,10,10,10,11,12,12,12,12,12,13,14,14,
%T 14,14,15,15,15,16,16,16,16,17,18,18,18,18,18,18,19,20,20,20,20,20,20,
%U 21,21,21,21,22,22,22,22
%N Numbers x such that xy/(x+y) is an integer for integers y=x,x+1,..n.
%C xy/(x+y) is the side of the inscribed square of a right triangle with integer legs x and y.
%e x=20,y=5, 100/25 = integer 4.
%o (PARI) xydivxpy(n) = { for(x=1,n, for(y=x,n, h=x*y/(x+y); if(h==floor(h), print1(x","); ) ) ) }
%K nonn
%O 1,1
%A _Cino Hilliard_, Dec 02 2003, corrected Nov 23 2006
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