Project Euler 1 - Multiples of 3 & 5
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.
Official link: https://projecteuler.net/problem=1
Notice if a number is divisible by 3 and 5 it is divisible by 15, we must make sure not to double count
Use arthmetic sequence to produce the sum of
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