<?php 
 
    require_once 'Combinatorics.php'; 
 
    $combinatorics = new Math_Combinatorics; 
    $set = range(0, 9); 
     
    $asc_num = 97; 
    while ($asc_num<= 122) { 
        # code... 
        array_push($set, chr($asc_num)); 
        $asc_num++; 
    } 
 
    //?? 
    echo $combinations = $combinatorics->combinations($set, 16); 
    //?? 
    //$permutations = $combinatorics->permutations($set, 16); 
?> 
 
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