Let $Q$ be a finite set of points in the plane. For any set $P$ of points inthe plane, $S_{Q}(P)$ denotes the number of similar copies of $Q$ contained in$P$. For a fixed $n$, Erd\H{o}s and Purdy asked to determine the maximumpossible value of $S_{Q}(P)$, denoted by $S_{Q}(n)$, over all sets $P$ of $n$points in the plane. We consider this problem when $Q=\triangle$ is the set ofvertices of an isosceles right triangle. We give exact solutions when $n\leq9$,and provide new upper and lower bounds for $S_{\triangle}(n)$.
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机译:令$ Q $为平面中的有限点集。对于飞机上任何一组$ P $的点,$ S_ {Q}(P)$表示$ P $中包含的$ Q $相似副本的数量。对于固定的$ n $,Erd \ H {o} s和Purdy要求确定所有集合$ P上的$ S_ {Q}(P)$的最大可能值,用$ S_ {Q}(n)$表示飞机上的$ n $$点。当$ Q = \ triangle $是等腰直角三角形的顶点集时,我们考虑这个问题。我们给出$ n \ leq9 $时的精确解,并为$ S _ {\ triangle}(n)$提供新的上下限。
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