Uniform convergence symbol (arrow on top of arrow, same size)

Question

I am looking for a symbol that looks like two arrows of the same size, one on top of the other with (possibly) a letter on top, this is my paint sketch of it:

I've tried something like

\xrightarrow{\xrightarrow{n}}

and similar combinations but it always makes one arrow smaller.

I've seen this symbol used to say that a sequence of functions converges uniformly to another function.

Answer 1

If you don't need it in smaller math styles, then this could work...

\documentclass{article}
\usepackage{stackengine,graphicx}
\stackMath
\newcommand\frightarrow{\scalebox{1}[.4]{$\rightarrow$}}
\newcommand\darrow[1][]{\mathrel{\stackon[1pt]{\stackanchor[1pt]{\frightarrow}{\frightarrow}}{\scriptstyle#1}}}
\begin{document}
$A\darrow[n] B$
\end{document}

Here is a composite alternative

\documentclass{article}
\usepackage{stackengine,graphicx,amssymb}
\stackMath
\newcommand\frightarrow{\scalebox{1}[.3]{$\rule[.45ex]{2ex}{1.5pt}%
  \kern-.2ex{\blacktriangleright}$}}
\newcommand\darrow[1][]{\mathrel{\stackon[1pt]{\stackanchor[1pt]{\frightarrow}{\frightarrow}}{\scriptstyle#1}}}
\begin{document}
$A\darrow[n] B$
\end{document}

Answer 2

With the amssymb package you can just use \rightrightarrows:

\documentclass[a4paper,12pt]{article}
\usepackage{mathtools,amssymb}
\begin{document}
\[A\overset{n}{\rightrightarrows}B\]
\end{document}

Answer 3

"Cheating" would be writing it as

f_n(x)^\rightarrow_\rightarrow f(x)

which results in the following formula: