# singly embedded sum and product signs

I deal with a lot of double sums / double products. I would like to be able to massage TeX into producing something like this:

(that was made with the gimp) ... and a product in product symbol as well.

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You can have a look at the section Joining and overlapping existing symbols in manual of Comprehensive Symbol List.

\documentclass{article}

\begin{document}

\newcommand\SUM{\mathop{%
\ooalign{%
\hfil$\displaystyle\sum$\cr
\hfil$\textstyle\sum$\cr}}}

$\SUM A_i$

\end{document}

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excellent, thanks. – Owen Maresh Feb 19 '11 at 16:08

For what it is worth, Unicode defines

⅀ U+2140 DOUBLE-STRUCK N-ARY SUMMATION

If you are able to use unicode-math (with XeLaTeX or LuaLaTeX) and appropriate math fonts, you can access that symbol with \mathbb{\sum}.

STIX/XITS Math gives and Cambria Math gives .

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