pzbagel++, I was about to say the same.

The formula, and today's value for NORM, are taken from Voting/Experience System.

#!/usr/bin/perl -w
use strict;
# Average XP for a number of ++ votes, with no -- votes, given a NORM.
my $votes = 50;
my $NORM  = 10.7453;
my @val   = (0, 1/3, 1/2, 2/3, 3/4, 1);
my $xp    = 0;
foreach my $rep ( 1 .. $votes ) {
  foreach (1..$#val) {
    $xp += $val[$_], last if $rep <= $_ * $NORM;
  }
}
printf "XP = %.1f\n", $xp;
[download]

XP = 31.7