#!/usr/bin/env perl
#
# collatz - print n and collatz(n) for each positive n
#
# $Id$

use warnings;
use strict;

$| = 1;  # unbuffer output

my %c = (1 => 1);  # caches the results

for (my $i = 1; 1; ++$i)
{
  my ($n,$c) = ($i,1);

  if (!$c{$n})
  {
    while (!$c{$n})
    {
      $n = $n % 2 ? 3*$n + 1 : $n / 2;
      ++$c;
    }
    $c{$n} = $c;
  }
  print "$i $c\n";
}