# Can't write the set-operator in mathjax?

When trying to write $$\{1,2,3\}$$ in a question on math.stackexchange.com it just becomes $$1,2,3$$. However it seems to work here on meta.math.stackexchange.com. How can I get it to work on the main-site?

The preview of the post has also become very slow lately. Maybe it is connected?

• Are you sure you used \{ and \} to get the delimiters? I cannot reproduce the problem. It works just as it should for me. – Jyrki Lahtonen Nov 15 at 20:58
• @JyrkiLahtonen I would think so since the OP were able to write this question correctly and compare both effects. I think it happened to me several times that the browser refuses to understand MathJax and became slow - but in that case iirc I would see the whole code, ie including both \ and {. – Arnaud Mortier Nov 15 at 22:32
• Thanks @ArnaudMortier. I apologize for jumping the gun. May be this is one of those situations, where reloading the page is necessary? Rethinking, I may have experienced similar problems. I don't remember this particular one. Anyway, reloading usually helped with those. – Jyrki Lahtonen Nov 15 at 22:34
• Do you have a link to an example of a post on main where this happened? Or is this just in the preview? – Martin Sleziak Nov 16 at 4:47
• I tried to do it again and it seems to work now. It was just in a preview it happened. Lately the previews have been very slow on the main site, but here on meta they seem to work fast. I guess it is easier to write tge post on meta and then just copy it when it is done. – user394334 Nov 16 at 10:11
• I’ve had the issue of some symbols not rendering properly on my browser lately. I believe this is what is happening to the OP. Refreshing the page seems to fix the problem. – Theoretical Economist Nov 16 at 11:50