All possible rectangle		Width
		$\color{lightseagreen} 1$	$\color{lightseagreen} 2$	$\color{lightseagreen} 3$	$\color{lightseagreen} 4$

Height	$\color{violet} 1$
	$\color{violet} 2$
	$\color{violet} 3$			$\color{violet} 3 \times \color{lightseagreen} 3$	$\color{violet} 3 \times \color{lightseagreen} 4$
	$\color{violet} 4$			$\color{violet} 4 \times \color{lightseagreen} 3$	$\color{violet} 4 \times \color{lightseagreen} 4$

Area of rectangle	$\color{lightseagreen}{1}$	$\color{lightseagreen}{2}$	$\color{lightseagreen}{3}$	$\color{lightseagreen}{4}$
Area of rectangle
$\color{violet}{1}$	$\color{violet}{1} \times \color{lightseagreen}{1}$	$\color{violet}{1} \times \color{lightseagreen}{2}$	$\color{violet}{1} \times \color{lightseagreen}{3}$	$\color{violet}{1} \times \color{lightseagreen}{4}$
$\color{violet}{2}$	$\color{violet}{2} \times \color{lightseagreen}{1}$	$\color{violet}{2} \times \color{lightseagreen}{2}$	$\color{violet}{2} \times \color{lightseagreen}{3}$	$\color{violet}{2} \times \color{lightseagreen}{4}$
$\color{violet}{3}$	$\color{violet}{3} \times \color{lightseagreen}{1}$	$\color{violet}{3} \times \color{lightseagreen}{2}$	$\color{violet}{3} \times \color{lightseagreen}{3}$	$\color{violet}{3} \times \color{lightseagreen}{4}$
$\color{violet}{4}$	$\color{violet}{4} \times \color{lightseagreen}{1}$	$\color{violet}{4} \times \color{lightseagreen}{2}$	$\color{violet}{4} \times \color{lightseagreen}{3}$	$\color{violet}{4} \times \color{lightseagreen}{4}$

Number of rectangle	$\color{lightseagreen}{n}$	$\color{lightseagreen}{n-1}$	$\color{lightseagreen}{n-2}$	$\color{lightseagreen}{n-3}$
Number of rectangle
$\color{violet}{n}$	$\color{violet}{n} \times \color{lightseagreen}{n}$	$\color{violet}{n} \times \color{lightseagreen}{n-1}$	$\color{violet}{n} \times \color{lightseagreen}{n-2}$	$\color{violet}{n} \times \color{lightseagreen}{n-3}$
$\color{violet}{n-1}$	$\color{violet}{n-1} \times \color{lightseagreen}{n}$	$\color{violet}{n-1} \times \color{lightseagreen}{n-1}$	$\color{violet}{n-1} \times \color{lightseagreen}{n-2}$	$\color{violet}{n-1} \times \color{lightseagreen}{n-3}$
$\color{violet}{n-2}$	$\color{violet}{n-2} \times \color{lightseagreen}{n}$	$\color{violet}{n-2} \times \color{lightseagreen}{n-1}$	$\color{violet}{n-2} \times \color{lightseagreen}{n-2}$	$\color{violet}{n-2} \times \color{lightseagreen}{n-3}$
$\color{violet}{n-3}$	$\color{violet}{n-3} \times \color{lightseagreen}{n}$	$\color{violet}{n-3} \times \color{lightseagreen}{n-1}$	$\color{violet}{n-3} \times \color{lightseagreen}{n-2}$	$\color{violet}{n-3} \times \color{lightseagreen}{n-3}$

Sum of rectangle area	$\color{lightseagreen}{1 \times n }$	$\color{lightseagreen}{2 \times (n-1)}$	$\color{lightseagreen}{3 \times (n-2)}$	$\color{lightseagreen}{4 \times (n-3)}$
Sum of rectangle area
$\color{violet}{1 \times n}$	$\begin{gather} \color{violet}{1 \times n} \\ \times \\ \color{lightseagreen}{1 \times n } \end{gather}$	$\begin{gather} \color{violet}{1 \times n} \\ \times \\ \color{lightseagreen}{2 \times (n-1)} \end{gather}$	$\begin{gather} \color{violet}{1 \times n} \\ \times \\ \color{lightseagreen}{3 \times (n-2)} \end{gather}$	$\begin{gather} \color{violet}{1 \times n} \\ \times \\ \color{lightseagreen}{4 \times (n-3)} \end{gather}$
$\color{violet}{2 \times (n-1)}$	$\begin{gather} \color{violet}{2 \times (n-1)} \\ \times \\ \color{lightseagreen}{1 \times n } \end{gather}$	$\begin{gather} \color{violet}{2 \times (n-1)} \\ \times \\ \color{lightseagreen}{2 \times (n-1)} \end{gather}$	$\begin{gather} \color{violet}{2 \times (n-1)} \\ \times \\ \color{lightseagreen}{3 \times (n-2)} \end{gather}$	$\begin{gather} \color{violet}{2 \times (n-1)} \\ \times \\ \color{lightseagreen}{4 \times (n-3)} \end{gather}$
$\color{violet}{3 \times (n-2)}$	$\begin{gather} \color{violet}{3 \times (n-2)} \\ \times \\ \color{lightseagreen}{1 \times n } \end{gather}$	$\begin{gather} \color{violet}{3 \times (n-2)} \\ \times \\ \color{lightseagreen}{2 \times (n-1)} \end{gather}$	$\begin{gather} \color{violet}{3 \times (n-2)} \\ \times \\ \color{lightseagreen}{3 \times (n-2)} \end{gather}$	$\begin{gather} \color{violet}{3 \times (n-2)} \\ \times \\ \color{lightseagreen}{4 \times (n-3)} \end{gather}$
$\color{violet}{4 \times (n-3)}$	$\begin{gather} \color{violet}{4 \times (n-3)} \\ \times \\ \color{lightseagreen}{1 \times n } \end{gather}$	$\begin{gather} \color{violet}{4 \times (n-3)} \\ \times \\ \color{lightseagreen}{2 \times (n-1)} \end{gather}$	$\begin{gather} \color{violet}{4 \times (n-3)} \\ \times \\ \color{lightseagreen}{3 \times (n-2)} \end{gather}$	$\begin{gather} \color{violet}{4 \times (n-3)} \\ \times \\ \color{lightseagreen}{4 \times (n-3)} \end{gather}$

Sum of rectangle area	$\color{lightseagreen}{1 \times n }$	$\color{lightseagreen}{2 \times (n-1)}$	$\color{lightseagreen}{3 \times (n-2)}$	$\color{lightseagreen}{4 \times (n-3)}$
Sum of rectangle area
$\color{violet}{1 \times n}$	$\begin{gather} \color{violet}{1 \times n} \\ \times \\ \color{lightseagreen}{1 \times n } \end{gather}$	$\begin{gather} \color{violet}{1 \times n} \\ \times \\ \color{lightseagreen}{2 \times (n-1)} \end{gather}$	$\begin{gather} \color{violet}{1 \times n} \\ \times \\ \color{lightseagreen}{3 \times (n-2)} \end{gather}$	$\begin{gather} \color{violet}{1 \times n} \\ \times \\ \color{lightseagreen}{4 \times (n-3)} \end{gather}$
$\color{violet}{2 \times (n-1)}$	$\begin{gather} \color{violet}{2 \times (n-1)} \\ \times \\ \color{lightseagreen}{1 \times n } \end{gather}$	$\begin{gather} \color{violet}{2 \times (n-1)} \\ \times \\ \color{lightseagreen}{2 \times (n-1)} \end{gather}$	$\begin{gather} \color{violet}{2 \times (n-1)} \\ \times \\ \color{lightseagreen}{3 \times (n-2)} \end{gather}$	$\begin{gather} \color{violet}{2 \times (n-1)} \\ \times \\ \color{lightseagreen}{4 \times (n-3)} \end{gather}$
$\color{violet}{3 \times (n-2)}$	$\begin{gather} \color{violet}{3 \times (n-2)} \\ \times \\ \color{lightseagreen}{1 \times n } \end{gather}$	$\begin{gather} \color{violet}{3 \times (n-2)} \\ \times \\ \color{lightseagreen}{2 \times (n-1)} \end{gather}$	$\begin{gather} \color{violet}{3 \times (n-2)} \\ \times \\ \color{lightseagreen}{3 \times (n-2)} \end{gather}$	$\begin{gather} \color{violet}{3 \times (n-2)} \\ \times \\ \color{lightseagreen}{4 \times (n-3)} \end{gather}$
$\color{violet}{4 \times (n-3)}$	$\begin{gather} \color{violet}{4 \times (n-3)} \\ \times \\ \color{lightseagreen}{1 \times n } \end{gather}$	$\begin{gather} \color{violet}{4 \times (n-3)} \\ \times \\ \color{lightseagreen}{2 \times (n-1)} \end{gather}$	$\begin{gather} \color{violet}{4 \times (n-3)} \\ \times \\ \color{lightseagreen}{3 \times (n-2)} \end{gather}$	$\begin{gather} \color{violet}{4 \times (n-3)} \\ \times \\ \color{lightseagreen}{4 \times (n-3)} \end{gather}$