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.

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Thought Process

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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