\usepackage[top=
1.6cm, bottom=
1.6cm, left=
1.6cm, right=
1.6cm
]{geometry
}
\newcommand\genkoyoshi[4]{% maxrow, maxcol, size, sep
\pgfmathsetmacro{\inc}{\size+
\sep}
\foreach \col in
{1,...,
\maxcol}{
\foreach \row in
{1,...,
\maxrow}{
\draw (
{(
\col-
1)*
\inc pt
},
{\row*
\size})
rectangle ++ (
\size,
\size);
\draw (
{(
\col-
1)*
\inc-
\sep},
{\size})
rectangle ++ (
\sep,
\maxrow*
\size);
\genkoyoshi{20}{20}{9mm
}{3mm
}