If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.
Find the sum of all the multiples of 3 or 5 below 1000.
console.log([...Array(1000).keys()]
.filter(n => n % 3 === 0 || n % 5 === 0)
.reduce((acc, n) => acc + n));