documentclass[border=10pt]{standalone}
usepackage{forest}
begin{document}
begin{forest}
   div2/.style={
    append/.process={ Ow+PS _>? l_w2 {content}{int(floor(##1/2)){1}{div2}{}{[##1,##2]}},
    },
   [10, div2]
end{forest}
end{document}

documentclass[border=10pt]{standalone}
usepackage{forest}
begin{document}
begin{forest}
  divn/.style args={1} ={
        append/.process={ Ow+PS _>? l_w2 {content}
{int(floor(##1/#1))}{1}{divn}{}{[##1,##2]}},
  },
  %
  tempcounta = {1},
  branches/.style={
     until{2*tempcounta > content}{
        divn={content},
        tempcounta/.pgfmath={tempcounta+1},
     },
  },
  %
  %
[3, branches]
end{forest}
end{document}