Fix ~ -> _

Author: ymd-h

site/site.org

@@ -631,8 +631,8 @@ In RER, equally strided transitions are sampled from the latest
 transition. The next sample contains one step older transions.
 
 \[ \begin{align}
-B_1 &= \lbrace& T_{t}  &, T_{t-stride}  &, \dots &, T_{t-batch~size \times stride}     &\rbrace \\
-B_2 &= \lbrace& T_{t-1}&, T_{t-stride-1}&, \dots &, T_{t-batch~size \times stride - 1} &\rbrace \\
+B_1 &= \lbrace& T_{t}  &, T_{t-stride}  &, \dots &, T_{t-batch_size \times stride}     &\rbrace \\
+B_2 &= \lbrace& T_{t-1}&, T_{t-stride-1}&, \dots &, T_{t-batch_size \times stride - 1} &\rbrace \\
 &\vdots&&&&&&
 \end{align} \]