Category:Pages using Math with unknown parameters

{{Unknown parameters category|1=Math}}

Note: the following code habit is not an error.

:{{math|{1, 2, 3}{{bg|yellow|{{!}}}}}} is not an error, and should be left unedited.

:In code: the indices can range over the set {{math|{1, 2, 3}|}}

:Text shown: "... the indices can range over the set {{math|{1, 2, 3}|}}"

The extra pipe symbol in {{math|{1, 2, 3}{{bg|yellow|{{!}}}}}} is unused but does not corrupt the math text. It helps understanding the input text (distinguishing the various }-symbol).

It produces a categorisation here, and a Warning: "{{red|1=unknown parameter {{!}}2=}}". However, since it is helpful, it is not an error, and it should not be edited out. {{As of|Jan 2021}}, 18 articles are listed with this feature.