Using an approximation to Stirling's series: 
use constant PI => 3.141592653589793238;
...
sub factorial {
  my $n = shift;
  return (sqrt((2*$n + 1/3)*PI)*($n**$n)*exp(-$n));
}

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In reply to Re: Pascal triange... by gumby
in thread Pascal's triangle... by kiat

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