# How do you make an arbitrary capital Greek letter behave like the \sum command? [duplicate]

My question is simple. I'm using a rarely used operation which requires a rarely used Greek symbol to represent it. My current way of writing it when written out in basic LaTex looks like

$$\Omega_{j=0}^\infty \phi_j$$


Which attaches the \{j = 0\} part to the lower right and the {\infty} to the upper right of the Greek symbol \Omega.

My trouble is simple. I want it to look like how it looks when we type

$$\sum_{j=0}^\infty \phi_j$$


Except with the capital Sigma replaced with a capital Omega.

That is, I want the {j=0} to appear directly below the \Omega and the {\infty} to appear directly above the \Omega. I also want the \Omega to appear as largely as the \Sigma appears in $$\sum$$.

Is this possible?

Disclaimer: I've never posted here before so I'm wary of the format of my question; I'm not sure if this matches the guidelines. I'm happy to edit if necessary.

• Try \DeclareMathOperator*{\OmSum}{\Omega} and load amsmath before. – user121799 Jul 24 '18 at 5:56
• Thanks I'll try that! I hope my question wasn't too trivial! – james.nixon Jul 24 '18 at 5:58
• – user94293 Jul 24 '18 at 6:06