\documentclass{article}
\usepackage{expl3,xparse}

% nur LaTeX2e:
\makeatletter
\newcounter{tmp}

% nicht expandierbar:
\newcommand\verfielfacheA[2]{%
  \setcounter{tmp}{#1}%
  \ifnum\value{tmp}>0
    #2%
    \addtocounter{tmp}{-1}%
    \expandafter\@firstofone
  \else
    \expandafter\@gobble
  \fi
  {\verfielfacheA{\value{tmp}}{#2}}%
}

% nicht expandierbar:
\newcommand\verfielfacheB[2]{%
  \setcounter{tmp}{#1}%
  \@whilenum{\value{tmp}>0}\do{#2\addtocounter{tmp}{-1}}%
}

% expandierbar:
\newcommand\verfielfacheC[2]{%
  \ifnum#1>0
    \expandafter\@firstofone
  \else
    \expandafter\@gobble
  \fi
  {#2\expandafter\verfielfacheC\expandafter{\the\numexpr#1-1\relax}{#2}}%
}
\makeatother

% mit expl3 und xparse, expandierbar:
\ExplSyntaxOn
\cs_new:Npn \jeff_multiplicate:nn #1#2
  { \prg_replicate:nn {#1} {#2} }
\DeclareExpandableDocumentCommand \verfielfacheD {mm}
  { \jeff_multiplicate:nn {#1} {#2} }
\ExplSyntaxOff

\begin{document}

+\verfielfacheA{3}{/t}+
+\verfielfacheB{3}{/t}+
+\verfielfacheC{3}{/t}+
+\verfielfacheD{3}{/t}+

\end{document}

\newcount\printcount
\def\multiprint#1#2{
  \printcount=0
  \loop\ifnum\printcount<#1
    #2%
  \advance\printcount by 1\repeat
}
\multiprint{33}{/t}
\bye