[Tex/LaTex] faster way to type sequences

bracketsmath-mode

When I'm using sequences in an article, I always type things like (x_n)_n and (x_n^k)_n. However, that doesn't display the subscript after the brackets very nicely. I know that I can fix this by using \left( and \right), but I forget about them most of the time (causing a lot of frustrations when I discover it after I printed my document).

\documentclass[]{article}

\begin{document}
These sequences aren't displayed perfectly:
$$(x_n)_n \qquad (x_n^k)_n.$$
These ones look okay:
$$\left(x_n\right)_n \qquad \left(x_n^k\right)_n.$$

\end{document}

Maybe it's because I find the use of \left( and \right) a bit too time-consuming. I'm therefore wondering whether there's a clean way to achieve the same thing somewhat faster.

(I'd find it no offence if you simply answer that I shouldn't be that forgetful… 😉 )

Best Answer

Don't use $$ in LaTeX, unless you aren't doing mathematics (there are certain situations where this can come handy, but definitely not for typesetting math displays).

In the first display, the outer subscript is level with the inner one, but not the second, because of the superscript. You solve the problem by typing

\[
(x^{k}_{n})^{}_{n}
\]

Example:

\documentclass{article}

\begin{document}
These sequences are displayed perfectly:
\[
(x_{n})_{n} \qquad (x_{n}^{k})^{}_{n}.
\]
These ones don't look okay:
\[
\left(x_{n}\right)_{n} \qquad \left(x_{n}^{k}\right)_{n}.
\]

\end{document}

enter image description here

Why aren't the items in the second display good? The outer subscript is too low (at least in my opinion) and the parentheses in the second case are too big.

If you want the outer subscript a bit lower, the best way is with braces:

\[
{(x_{n})}_{n} \qquad {(x_{n}^{k})}_{n}.
\]

enter image description here

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