# 平方數

1, 4, 9, 16, 25, 36, 49, 64, ......之間嘅差成等差數列 ${\displaystyle 64-15=49}$, ${\displaystyle 49-13=36}$, ${\displaystyle 36-11=25}$, ${\displaystyle 25-9=16}$, ${\displaystyle 16-7=9}$, ${\displaystyle 9-5=4}$, ${\displaystyle 4-3=1}$