How to write larger \natural symbol?

Question

If we want to write big \sum symbol, we can write $\sum\limits_{i=1}^n x_i$.

I want to do similar thing for \natural symbol which will be used to denote the boundary connected sum.

How can I do this?

Answer 1

Saying \limits does not increase the size of the summation symbol, it just moves the limits.

\documentclass{article}
\usepackage{amsmath}
\begin{document}
$\sum\limits_{i=1}^n$ \quad $\sum_{i=1}^n$ \quad
\end{document}

If you want to do the same with the \natural symbol you need to use \mathop.

$\natural_{i=1}^n$ \quad $\mathop\natural\limits_{i-1}^n$

If you actually want a larger \natural you can create one with \large, \Large, etc.

\[ \mathop{\hbox{\Large$\natural$}}\limits_{i=1}^n \natural \]

You could also use \scalebox from the graphicx package.

Answer 2

\newcommand{\bignatural}{\mathop{\mathchoice
  {\vcenter{\hbox{\LARGE$\natural$}}}
  {\vcenter{\hbox{\large$\natural$}}}
  {\vcenter{\hbox{\footnotesize$\natural$}}}
  {\vcenter{\hbox{\scriptsize$\natural$}}}
}\displaylimits}

Here are examples in the four styles (the \sum is for comparison; load amsmath for correctly scaling the big operators in script styles)