How to vertically align each comma in the following 2 identical sequences?

Question

The following output seems to be difficult to look up an item in the upper sequence with its corresponding item in the lower sequence as the commas are not vertically aligned.

\documentclass[preview,border=12pt,varwidth]{standalone}
\usepackage{amsmath}
\begin{document}
\abovedisplayskip=0pt\relax
\begin{align*}
\{a_n\}
&=
\{1^2, 1^2 +2^2, 1^2 +2^2 +3^2, 1^2 +2^2 +3^2 +4^2, \dotsc\}\\
&=
\{1, 5, 14, 30, \dotsc\}
\end{align*}
\end{document}

enter image description here

I want to align each comma in the upper and lower sequence. How to do it elegantly (that consumes less keystrokes)?

score 14 · Answer 1 · answered Nov 19 '13 at 18:11

14

I understand that this does not answer your question in the strict sense, but in my opinion the output is clearer:

\documentclass[border=12pt,varwidth]{standalone}
\usepackage{amsmath}

\begin{document}
\begin{equation}
     \{a_n\} = \{\overbrace{1^2}^1,
                 \overbrace{1^2+2^2}^5,
                 \overbrace{1^2 +2^2 +3^2}^{14},
                 \overbrace{1^2 +2^2 +3^2 +4^2}^{30},\dotsc \}
\end{equation}
\end{document}

answered Nov 19 '13 at 18:11

A nice idea and make the code tidier. – kiss my armpit Nov 19 '13 at 18:15
You could probably also do it with \underbrace, making the output closer to what th OP intended. On the other hand this looks much better than any of the "valid" solutions – SztupY Nov 19 '13 at 21:47

score 10 · Accepted Answer · edited Apr 03 '17 at 00:15

A few ideas with alignedat (since this is only one formula I am using equation) and one with array for centered aligning which otherwise would need more work to be able to be usable in one of the *align* environments.

Code

\documentclass[border=12pt,varwidth]{standalone}
\usepackage{amsmath,array}
\begin{document}

\begin{equation}
\begin{alignedat}{5}
\{a_n\} &= \{1^2 &&, 1^2 +2^2 &&, 1^2 +2^2 +3^2 &&, 1^2 +2^2 +3^2 +4^2 &&, \dotsc\} \\
        &= \{1   &&, 5        &&, 14            &&, 30                 &&, \dotsc\}
\end{alignedat}
\end{equation}

\begin{equation}
\renewcommand*\c{,{}}%
\begin{alignedat}{5}
\{a_n\} &= \{1^2 \c && 1^2 +2^2 \c && 1^2 +2^2 +3^2 \c && 1^2 +2^2 +3^2 +4^2 \c & \dotsc\} \\
        &= \{1   \c && 5        \c && 14            \c && 30                 \c & \dotsc\}
\end{alignedat}
\end{equation}


\begin{equation}
\renewcommand*\c{,{}}%
\begin{alignedat}{6}
\{a_n\} &= \{& 1^2 \c && 1^2 +2^2 \c && 1^2 +2^2 +3^2 \c && 1^2 +2^2 +3^2 +4^2 \c && \dotsc\} \\
        &= \{& 1   \c && 5        \c && 14            \c && 30                 \c && \dotsc\}
\end{alignedat}
\end{equation}

\begin{equation}
 \begin{array}{@{}r@{} *4{c@{,{}}} l@{}}
     \{a_n\} = \{ & 1^2 & 1^2 +2^2 & 1^2 +2^2 +3^2 & 1^2 +2^2 +3^2 +4^2 & \dotsc\} \\[\jot]
             = \{ & 1   & 5        & 14            & 30                 & \dotsc\}
  \end{array}
\end{equation}
\end{document}

Output

enter image description here

@DonutE.Knot The space (it’s a \dimen) between math-mode lines. It is defined by LaTeX and set to 3pt. For reference, see Increase spacing in split environment. — Qrrbrbirlbel, Nov 19 '13 at 17:43

score 7 · Answer 3 · edited Apr 03 '17 at 00:13

A contest? ;-)

\documentclass{article}
\usepackage{amsmath}
\makeatletter
\newcommand{\alignedset}[2][l]{%
  \vcenter{
    \everymath\expandafter{\the\everymath\displaystyle}
    \m@th\let\\\@tabularcr\openup1\jot
    \ialign{\hfil$##$&${}##{}$\hfil&&
            \if#1l\hfilneg\fi\hfil
            $##{}$%
            \if#1r\hfilneg\fi\hfil
            \cr#2\crcr}
    }%
}
\makeatother
\begin{document}
\begin{equation}
\alignedset{
  \{a_n\} &= \{ & 1^2, & 1^2+2^2, & 1^2+2^2+3^2, & 1^2+2^2+3^2+4^2, & \dotsc \} \\
          &= \{ & 1,   & 5,       & 14,          & 30,              & \dotsc\}
}
\end{equation}
\begin{equation}
\alignedset[c]{
  \{a_n\} &= \{ & 1^2, & 1^2+2^2, & 1^2+2^2+3^2, & 1^2+2^2+3^2+4^2, & \dotsc \} \\
          &= \{ & 1,   & 5,       & 14,          & 30,              & \dotsc\}
}
\end{equation}
\begin{equation}
\alignedset[r]{
  \{a_n\} &= \{ & 1^2, & 1^2+2^2, & 1^2+2^2+3^2, & 1^2+2^2+3^2+4^2, & \dotsc \} \\
          &= \{ & 1,   & 5,       & 14,          & 30,              & \dotsc\}
}
\end{equation}
\end{document}

enter image description here

quasi pure Plain TeX were it not for \let\\\@tabularcr, are you abandoning LaTeX3 ? :) — , Nov 19 '13 at 21:14

score 4 · Answer 4 · edited Apr 13 '17 at 12:34

Using the (experimental) tabstackengine package given at Measuring align

\documentclass[preview,border=12pt,varwidth]{standalone}
\usepackage{amsmath}
\usepackage{tabstackengine}
\stackMath
\begin{document}
\renewcommand\stackalignment{l}
\tabbedstackunder{%
\{a_n\}
&=
\{1^2&, 1^2 +2^2&, 1^2 +2^2 +3^2&, 1^2 +2^2 +3^2 +4^2&, \dotsc\}%
}{%
&=
\{1&, 5&, 14&, 30&, \dotsc\}}
\end{document}

enter image description here

To put all 3 alignment choices into a single macro, with the inter-equation gap set to 10pt, and the inter-line gap set to 3pt:

\documentclass[preview,border=12pt,varwidth]{standalone}
\usepackage{amsmath}
\usepackage{tabstackengine}
\stackMath
\begin{document}
\setstackgap{S}{10pt}
\renewcommand\stackalignment{l}
\Shortstack{
\tabbedstackunder[3pt]{%
\{a_n\}
&=
\{1^2&, 1^2 +2^2&, 1^2 +2^2 +3^2&, 1^2 +2^2 +3^2 +4^2&,& \dotsc\}%
}{%
&=\{1&, 5&, 14&, 30&,& \dotsc\}}
\\
\renewcommand\stackalignment{c}
\tabbedstackunder[3pt]{%
\{a_n\}
&=&
\{&1^2&,& 1^2 +2^2&,& 1^2 +2^2 +3^2&,& 1^2 +2^2 +3^2 +4^2&,& \dotsc\}%
}{%
&=&\{&1&,& 5&,& 14&,& 30&,& \dotsc\}}
\\
\renewcommand\stackalignment{r}
\tabbedstackunder[3pt]{%
\{a_n\}
=&
\{&1^2,& 1^2 +2^2,& 1^2 +2^2 +3^2,& 1^2 +2^2 +3^2 +4^2,& \dotsc\}%
}{%
=&\{&1,& 5,& 14,& 30,& \dotsc\}}
}
\end{document}

enter image description here

@DonutE.Knot Sorry, I had to head out after posting. Correction applied. — Steven B. Segletes, Nov 19 '13 at 18:20

How to vertically align each comma in the following 2 identical sequences?

4 Answers4

Code

Output