I don't think there's a native function for random numbers in Vimscript.
A way using :python (use it in a function, perhaps, with 10000 and 60 replaced by parameters):
:python <<EOF import vim import random line = vim.current.window.cursor[0] r = getattr(__builtins__, 'xrange', range) # To make it work for both Python 2 & 3 vim.current.buffer[line:line] = list(map(str, random.sample(r(10000), 60))) EOF See my answer to Making a box in vim via pythonMaking a box in vim via python for a quick intro on Python scripting in Vim.
Since vim.current.buffer is a list of strings, we can assign a list of strings to it the way we would in Python. random.sample is just the simplest way I can think of to get a list of random integers in Python.