大家在查： squeezed state Sravasti Src homology domain Sri Aurobindo SRIFFI Square Root of 2 Square opening square numbers Squamous metaplasia squamous epithelium

squaring the square

squaring the square

　　4.最小的完美正方形（Squaring the square）包含21个子正方形。　　5.高度为3的二进制树（Binary tree）有21种。