   <mi mathvariant="italic">a</mi>
                                    <mo>⁢</mo>
                                    <mfenced open="&#x2308;" close="&#x2309;">
                                        <mfrac>
                                            <mfenced open="" close="">
                                                <mrow>
                                                    <mi mathvariant="italic">n</mi>
                                                    <mo>⁢</mo>
                          