I want to write:

$\cup_{n \in \mathbb{N}}$, and $\sum_{i=n}^\mathbb{N}$. But I want them the index to be above and below the symbol, not to the side, how do I fix this?

  • $\begingroup$ Let me just say that using $\mathbb N$ as the upper bound for a sum is very unusual. I'd say that $\sum\limits_{i=n}^N$ or $\sum\limits_{i=n}^\infty$ are what I would have expected there. $\endgroup$ Commented Apr 29, 2014 at 6:56
  • $\begingroup$ @Martin: Or $\sum\limits_{n\in\Bbb N}$. $\endgroup$
    – Asaf Karagila Mod
    Commented Apr 29, 2014 at 6:57
  • $\begingroup$ Please avoid doing this in titles. It takes too much vertical space on the homepage, and it's unfair to others. $\endgroup$ Commented Apr 29, 2014 at 11:45
  • $\begingroup$ To expand on what @AymanHourieh wrote: There is a post about Guidelines for good use of $\LaTeX$ in question titles $\endgroup$ Commented Apr 29, 2014 at 12:22

1 Answer 1


You can use \limits to get that as in $\sum\limits_{i=n}^\mathbb{N}\frac1{i^2}$. However, this severely messes with the interline spacing.

code: \sum\limits_{i=n}^\mathbb{N}\frac1{i^2}

You can also use \displaystyle as in $\displaystyle\sum_{i=n}^\mathbb{N}\frac1{i^2}$. However, this really messes with interline spacing.

code: \displaystyle\sum_{i=n}^\mathbb{N}\frac1{i^2}

  • $\begingroup$ Considering the examples in the OP, it is also worth mentioning that \cup cannot be used together with limits, one has to use \bigcup instead: $\bigcup\limits_{n\in\mathbb N}$ $\bigcup\limits_{n\in\mathbb N}$. $\endgroup$ Commented Apr 28, 2014 at 17:07
  • $\begingroup$ @MartinSleziak: good point, I didn't notice they were using $\cup$. However, they could use $\operatorname{\cup}\limits_{i=1}^\infty$ or $\operatorname*{\cup}_{i=1}^\infty$. $\endgroup$
    – robjohn Mod
    Commented Apr 28, 2014 at 18:15

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