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.
link: https://projecteuler.net/problem=1
link: https://math.stackexchange.com/questions/9259/find-the-sum-of-all-the-multiples-of-3-or-5-below-1000