How to remove annoying header and footer for some pages that are intentionally made landscape?

Question

I am writing a book where some tables need wider space. The only solution is to make the tables in intentionally-made landscape pages.

Unfortunately, there are annoying headers and footers on the landscape pages. How to remove those annoying header and footers?

The following is my "minimal" code snippet:

\documentclass{book}
\usepackage[a4paper,margin=20mm]{geometry}
\usepackage{lscape}
\usepackage{lipsum}
\usepackage{calc}
\usepackage{longtable,array}

\begin{document}
\chapter{One}
\lipsum[1]
\section{One One}
\lipsum[2]

\pagestyle{empty}
\begin{landscape}
\begin{longtable}{|m{0.4\textwidth-2\tabcolsep-1.5\fboxrule}|m{0.6\textwidth-2\tabcolsep-1.5\fboxrule}|}
\hline
a & b\\\hline
c & d\\\hline
\end{longtable}
\end{landscape}
\pagestyle{plain}

\lipsum[3]
\end{document}

---

EDIT 1:

I made a correction in the column width, i.e., changing 2\fboxrule to 1.5\fboxrule. The former calculation is wrong because the rule between 2 columns should NOT be calculated twice. I slipped a little here.

---

EDIT 2:

Herbert's solution is the final answer.

Answer 1

\documentclass{article}
\usepackage{geometry}

\usepackage{lscape}

\begin{document}
foo
\clearpage\pagestyle{empty}
\begin{landscape}

bar\clearpage baz
\end{landscape}
\pagestyle{plain}

next page

\end{document}

Answer 2

You want to use \thispagestyle{empty} on the pages that shouldn't have headers or footers.

Edit:

\begin{landscape}
\thispagestyle{empty}
% longtable code
\end{landscape}