#!/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";
}