The nCr function above is horribly inaccurate. While n!/r!(n-r)! is indeed a valid formula for binomial coefficients, it's hardly a good way to calculate them. Here's a better way: 
sub nCr {
  my ($n, $r) = @_;
  my $res = 1;
  for my $i (1..$r) {
    $res *= $n--;
    $res /= $i;
  }
  $res;
}

[download]
Why $res remains an integer (for "reasonable" parameter values) remains an exercise for the reader...

In reply to Re: Binomial Expansion by ariels
in thread Binomial Expansion by crazyinsomniac

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