Arithmetic progression in LaTeX

Question

How the following image could be generated in LaTeX? It is an arithmetic progression.

I don't have any idea how to do it. Can you help me?

\documentclass[a4paper, 11pt]{article}
\begin{document}
$$\begin{array}{ccccccc}
-1, & 2, & 5, & 8, & 11, & 14, & 17,\ldots
\end{array}$$
\end{document}

Answer 1

I suggest you employ \underbracket, a macro provided by the mathtools package.

Speaking for myself, I think this expression would look better without the commas.

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{mathtools} % for '\underbracket' command
\newcommand\ub{{\underbracket[0.4pt]{,\quad}_{+3}}}
\begin{document}
[
-1\ub 2\ub 5\ub 8\ub 11\ub 14\ub 17,\dots
]
\end{document}

Answer 2

Using \foreach loops from TikZ, you can also make the whole thing automatic. In the following example, I defined a command \arithmeticprogression with four arguments:

1. (optional) The horizontal unit length of the tikzpicture, defaults to 1cm.
2. The starting point of the arithmetic progression.
3. The step in the progression.
4. The number of numbers that should be written in the progression.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{calc}
\usetikzlibrary{ext.paths.ortho}
\newcommand*{\APsign}{+}
\newcommand*{\arithmeticprogression}[4][1cm]{%
    \ifnum #3<0
        \renewcommand*{\APsign}{}
    \else
        \renewcommand*{\APsign}{+}
    \fi
    \begin{tikzpicture}[x=#1, every node/.style={inner xsep=0pt, inner ysep=1.5pt, anchor=base}]
        \foreach \x [evaluate=\x as \y using int(#2+(\x-1)*#3)] in {1, ..., #4}
            \node (\x) at (\x, 0) {$\y$\makebox[0pt][l]{,}};
        \foreach \x [evaluate=\x as \z using int(\x-1)] in {2, ..., #4}
            \draw[teal] (\z.south east) |-|[distance=-3pt] (\x.south west) node[midway, below, black] {$\APsign#3$};
        \node at ($(#4,0)+(1,0)$) {$\dots$};
    \end{tikzpicture}
}
\begin{document}
\arithmeticprogression{-1}{3}{7}
\arithmeticprogression{2}{4}{4}
\arithmeticprogression{1}{-2}{6}
\end{document}

Answer 3

A non-conventional use of tabularray:

\documentclass[a4paper, 11pt]{article}
\usepackage{xcolor}
\usepackage{tabularray}
\begin{document}
[
\begin{tblr}{
    colspec={*{15}{c}},
    columns={colsep=1pt},
    row{1,2}={rowsep=-4pt},
    row{3}={rowsep=2pt},
    cell{3}{even}={preto={+3}},
    hline{3}={even}{blue,wd=2pt},
    vline{2-Y}={2}{blue,wd=2pt}
    }
-1, && 2, && 5, && 8, && 11, && 14, && 17,&&\ldots\
&&&&&&&&&&&&&&\
&&&&&&&&&&&&&&\
\end{tblr}
]
\end{document}