This page is written by XHTML and may includes MathML, but I don't think your browser doesn't support XHTML.

Prease enter same page written by HTML.

Or you can move to XHTML/MathML page forcibly.

When your browser can show next XHTML page with MathML, please tell me bellow "Your agent" at here

Your user agent : CCBot/2.0 (https://commoncrawl.org/faq/)

HTML : http://pen.envr.tsukuba.ac.jp/~torarimon/?RPC

XHTML : http://pen.envr.tsukuba.ac.jp/~torarimon/?RPC=force_xhtml