# Underscore formatting bug, excited (maybe) by subscripts of nothing. [duplicate]

Possible Duplicate:
Matrices not rendered correctly

I'm trying to display old-style notations for combinations, that is, ${}_nC_r$ for the thing now typically written $n\choose r$. To get the "$n$" here you must put a subscript on an empty expression, thus: $\$${}_nC_r\$$. I can't get this to work correctly when the trailing subscript is multi-character. If I want$n\choose 11$and put the braces where I'd expect them, it comes out like this:${}_nC_{11}$. Note that I didn't quote anything; the system simply refuses to interpret the TeX. There's no problem if the first subscript is multi-character${}_{11}C_9$works OK. It looks like the problem is that one or t'other underscore obscures the trailing dollar sign, so math mode isn't exited properly. If I try the$n\choose 11$example again and include another math expression before the next paragraph break, it comes out like this:${}_nC_{11}$is zero by definition when$n<11$. ## marked as duplicate by kennytmNov 2 '10 at 16:57 This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question. • Use backslash, e.g. {}\\_nC\\_{11} ->${}\_nC\_{11}\$ to avoid Markdown interpreting the underscores as italic. – kennytm Nov 2 '10 at 17:06
• @KennyTM, why can't we escape text inside of the dollar signs like on MO (by allowing mathJax to render inside of code tags)? – 97832123 Nov 2 '10 at 21:54
• @978: that's what meta.math.stackexchange.com/questions/551/… is about, meh. – kennytm Nov 2 '10 at 22:26
• @KennyTM: I find your support for the status-quo incredibly frustrating. It's not hard to do, so just help us campaign for it. – 97832123 Nov 3 '10 at 7:01
• @978: What else you want to do? I've already filed a feature-request to mimic the MO behavior. I do not control the back-end, if the admins at SO Inc. decided it's not an issue there's nothing we can do. – kennytm Nov 3 '10 at 7:03
• @KennyTM: Did they decide that? If so, we should just keep bugging them about it until they do something (that is what we can do!). – 97832123 Nov 3 '10 at 12:01