Not brilliance, but not horrible for a first ( at least I hope?)

        for($i=1;$i<1000000;               $i++)
        {@.
                     [$i]=((
        $i+
                     $i+$i+$i+             $i)
        *                                   $i
        )/                  (5);            $
        _+=      (($.[$.[$.[               1]]]
        +$.[1])                             /2
        ) /$.                              [$i]
        ;}$_=                              sqrt
        ($_*                                ($.[
        2]+2)
        );print;
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