Tikz arithmetic progression

Question

I'm trying to do something like that to show a arithmetic progression (using TikZ):

Thanks! :D

Answer 1

With PSTricks.

\documentclass[preview,border=20pt]{standalone}
\usepackage{pst-node}
\psset{arm=8pt,arrows=->,nodesep=2pt,shortput=nab,labelsep=2pt}

\begin{document}
$
(\rnode{2}{2},\rnode{4}{4},\rnode{6}{6},\rnode{8}{8},\cdots)
\ncbar[angle=90]{2}{4}^{\scriptstyle 2}
\ncbar[angle=-90]{4}{6}_{\scriptstyle 2}
\ncbar[angle=90]{6}{8}^{\scriptstyle 2}
$
\end{document}

Answer 2

Remarks

For some unknown reason, when using the standalone documentclass an error

! Missing $ inserted.

is thrown.

Implementation

\documentclass{article}
\pagestyle{empty}
\usepackage{tikz}
\tikzset{every picture/.append style={remember picture}}
\begin{document}
$(
\tikz[baseline=(n2.base)]{\node (n2) {$2$};},
\tikz[baseline=(n4.base)]{\node (n4) {$4$};},
\tikz[baseline=(n6.base)]{\node (n6) {$6$};},
\tikz[baseline=(n8.base)]{\node (n8) {$8$};},
\cdots)
$
\begin{tikzpicture}[overlay]
    \path[->] (n2) edge[out=90,in=90] node[above] {$+2$} (n4);
    \path[->] (n4) edge[out=90,in=90] node[above] {$+2$} (n6);
    \path[->] (n6) edge[out=90,in=90] node[above] {$+2$} (n8);
\end{tikzpicture}

\vspace{1cm}

$(
\tikz[baseline=(n2.base)]{\node (n2) {$2$};},
\tikz[baseline=(n4.base)]{\node (n4) {$4$};},
\tikz[baseline=(n6.base)]{\node (n6) {$6$};},
\tikz[baseline=(n8.base)]{\node (n8) {$8$};},
\cdots)
$
\begin{tikzpicture}[overlay]
    \path[->] (n2) edge[out=90,in=90]   node[above] {$+2$} (n4);
    \path[->] (n4) edge[out=-90,in=-90] node[below] {$+2$} (n6);
    \path[->] (n6) edge[out=90,in=90]   node[above] {$+2$} (n8);
\end{tikzpicture}
\end{document}

Output

Answer 3

A solution using a variation of \tikzmark:

\documentclass{article}
\usepackage{tikz}

\newcommand\tikzmark[1]{\tikz[remember picture,baseline=(#1.base)]{\node(#1){#1};}}
\newcommand\arprog[3][bend left]{\tikz[remember picture,overlay,font=\footnotesize]{
    \draw[->,#1](#2.north)to node[above]{$+2$}(#3.north);
}}

\begin{document}

\[
  (\tikzmark{2},\tikzmark{4},\tikzmark{6},\dots)
\]

\arprog{2}{4}
\arprog{4}{6}

\end{document}