CodeEval competition - Predict The Number. Thanks to ferhatelmas/algo for the idea! Very interesting solution.

PredictTheNumber.php

<?php

$input = file_get_contents($argv[1]);
$rows = explode("\n", $input);

foreach($rows as $row) {
    if($row >= 0 && $row <= 3000000000) {

        $bin = decbin($row);
        $sum = 0;

        for($i = 0; $i < strlen($bin); $i++)
            if($bin[$i] == "1") $sum++;

        echo $sum % 3 . "\n";
    }
}

@samarthbhargav: the fomula can be searched from the OEIS, this link https://oeis.org/A071858