Diagram of a sequence

Question

Could you help me I have been looking for how to make a diagram similar to this image. Thanks.

Answer 1

Welcome to TeX.SE!!!

You can create a macro that draws the arcs above and below the vertical bars. If you want only one macro for both kind of arcs you need to change the axis locally, i.e. y=#3 cm in my example, where the argument #3 can take only values 1/-1.

A complete solution could be:

\documentclass[tikz,border=1cm]{standalone}
\newcommand{\myarc}[3] % start, end, 1/-1 (up, down) 
{
  \pgfmathsetmacro\l{int(#2-#1+1)} % label
  \draw[y=#3 cm,red] (#1-0.2,0.5) to[out=30*#3,in=150*#3] node[midway,yshift=#3*0.25cm] {$\l$} (#2+0.2,0.5) ;
}
\begin{document}
\begin{tikzpicture}[line cap=round]
% vertical bars
\foreach\i in {1,...,16}
  \draw[thick] (\i,-0.5) --++ (0,1);
% top arcs
\myarc {2} {5}{1}
\myarc {6} {9}{1}
\myarc{11}{14}{1}
\myarc{15}{16}{1}
% bottom arcs
\myarc {3} {6}{-1}
\myarc {8}{11}{-1}
\myarc{13}{15}{-1}
\end{tikzpicture}
\end{document}