Here is an example:
<\equation*>
\<ell\><rsup|p><around*|(|\<bbb-N\>|)>\<assign\><around*|{|<around*|(|a<rsub|1>,a<rsub|2>,\<ldots\>|)>\<in\>\<bbb-C\><rsup|\<bbb-N\>>\<barsuchthat\><big|sum><rsub|n=1><rsup|\<infty\>><around*|\||a<rsub|n>|\|><rsup|p>\<less\>+\<infty\>|}>
</equation*>
The size of the “such that” vertical bar is too small. I could change it to
<\equation*>
\<ell\><rsup|p><around*|(|\<bbb-N\>|)>\<assign\><around*|{|<around*|(|a<rsub|1>,a<rsub|2>,\<ldots\>|)>\<in\>\<bbb-C\><rsup|\<bbb-N\>><mid|\|><big|sum><rsub|n=1><rsup|\<infty\>><around*|\||a<rsub|n>|\|><rsup|p>\<less\>+\<infty\>|}>
</equation*>
but the spacing does not seem to be correct.