"Factorials"
Given the first few factorials:
1! = 1
2! = 2 x 1 = 2
3! = 3 x 2 x 1 = 6
4! = 4 x 3 x 2 x 1 = 24
What is the sum of the first 15 factorials, NOT INCLUDING 0!?
Once you realise you are summing the factors it makes this challenge a lot more manageable.
Awnser:
1401602636313
Source:
function factorial($number) {
if ($number < 2) {
return 1;
} else {
return ($number * factorial($number-1));
}
}
function solution(){
$solution = 1;
$factorial = 0;
for($addfactorial = 1; $addfactorial <= 15; $addfactorial++){
$solution += factorial($addfactorial);
}
echo $solution - 1;
}