Limit controls must follow a math operator

Question

I'm receiving "Limit controls must follow a math operator" error. Googled it, tried, nothing helped. Appears on Overleaf 2.0, using makefile in Cent OS, Fedora. Using pkgs geometry, amsmath, amsthm, amssymb, amsfonts, verbatim, babel (czech), inputenc (utf8), fontenc (IL2)

l.99 ...� $\lim\limits_{n\to\infty}$ a $\Pi\limits _{i=1}^n 2^i$...
I'm ignoring this misplaced \limits or \nolimits command.

The line looks like this:

... ${\lim_{x\to\infty}f(n)}$ ... $\Pi_{i=1}^n 2^i$ ... $\bigcup_{A\in B}A$... $\lim\limits_{n\to\infty}$ ... $\Pi\limits_{i=1}^n 2^i$ ... \verb|\limits|

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EDIT1: Found that problem starts at ${\Pi\limits_{i=1}^{n} 2^i}$. Unfortunately, i need \limits for \sum and \Pi or anything, that forces the \Pi to have compact form (n above, i=1 under), it's school homework :)

Any advice appreciated. Thx

Answer 1

\Pi is a symbol not an operator, you are probably looking for \prod which is the product operator (which uses \Pi as its symbol but has a different category).