Question

How to calculate the sum of series: 1/1! + 2/2! + 3/3! + 4/4! + ... N/N! in PHP

Answer 1

function factorial($n) {
    if ($n <= 1) {
        return (1);
    } else {
        $n = $n * factorial($n - 1);
    }
 
    return ($n);
}


echo "Calculate the sum of series: 1/1! + 2/2! + 3/3! + 4/4! ... + N/N!" . "\n";
 
$N = 5;
$sum = 0;
 
for ($i = 1; $i <= $N; $i++) {
    $sum +=  $i / factorial($i);
}

echo "sum = " . $sum;
 
 

  
/*
run:
    
Calculate the sum of series: 1/1! + 2/2! + 3/3! + 4/4! ... + N/N!
sum = 2.7083333333333
    
*/

 

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