The graphs of the equations
$$y=k, \qquad y=\sqrt{3}x+2k, \qquad y=-\sqrt{3}x+2k,$$
are drawn in the coordinate plane for \(k=-10,-9,-8,\ldots,9,10.\,\) These 63 lines cut part of the plane into equilateral triangles of side \(2/\sqrt{3}.\,\) How many such triangles are formed?
(第十二届AIME1994 第6题)