Show header rule after specific page

%% special thanks to Werner at https://tex.stackexchange.com/a/121988
%% based on is answer I removed the head rule from some undesired pages
%% the result is

\renewcommand{\headrulewidth}{\ifnum\value{page}>3 0.2pt\else 0pt\fi}

%% original code just shows page number after page 2

\fancyhead[L]{\ifnum\value{page}<2\relax\else\thepage\fi}