MathML generated by MathToWeb
A MathML example displaying the pairing delimiters ( and ) (normal parentheses) with \left and \right commands in place to auto-size them.

$\left(\genfrac{}{}{0.1ex}{}{A^2}{b_n}\right)$ $\left( \frac{A^2}{b_n} \right)$

<math xmlns="http://www.w3.org/1998/Math/MathML">
<mrow>
	<mo>(</mo>
	<mfrac linethickness="1">
		<mrow>
			<msup>
				<mi>A</mi>
				<mn>2</mn>
			</msup>
		</mrow>
		<mrow>
			<msub>
				<mi>b</mi>
				<mi>n</mi>
			</msub>
		</mrow>
	</mfrac>
	<mo>)</mo>
</mrow>
</math>