Task

The objective is to write a function that finds the sum of all positive multiples of 3 or 5 below n.

Show output for n = 1000.

This is is the same as Project Euler problem 1.

Extra credit: do this efficiently for n = 1e20 or higher.




#!/usr/bin/awk -f
{ 
	n = $1-1;
	print sum(n,3)+sum(n,5)-sum(n,15);
}
function sum(n,d) {
	m = int(n/d);
	return (d*m*(m+1)/2);
}