need help with a simple logic

Hi friends

i was trying to generate a simple mathematical series as follows

1
1,2
2,3,4
4,5,6,7
7,8,9,10,11

tried at least half a day with no result. i messed up everything, now its totally blank in my head

can any body help me on this

thanks in advance

PHP Code:

---

    function nrSum($index){
        $sum = 0;
        for($i=0; $i<=$index; $i++){
            $sum+=$i;
        }
        return $sum;
    }
    for($i=0; $i<10; $i++){
        $start = nrSum($i-1)+1;
        for($j=0; $j<=$i; $j++){
            echo ($start+$j).", ";
        }
        echo "<br />";
    } 


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Thank you very much hyperionXS

Actually I found a shorter one:

PHP Code:

---

    for($i=0; $i<10; $i++){
        $start = $i * ($i-1) / 2 + 1;
        for($j=0; $j<=$i; $j++){
            echo ($start+$j).", ";
        }
        echo "<br />";
    } 


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