So today I tackled a Euler problem that I had originally looked into several months back when I initially started exploring F#

Problem

2520 is the smallest number that can be divided by each of the numbers from 1 to 10 without any remainder.

What is the smallest positive number that is evenly divisible by all of the numbers from 1 to 20?

Solution

I decided on the brute force approach again. I believe that I could have worked with prime factors etc to have reached the solution a lot quicker – but haven’t had time to look properly into that approach.

Once again the unfold function played a big role – now that I understand it a bit better, it doesn’t look like as much black magic as it initially looked like. I would love to get any suggestions / examples of how other people have solved this problem using F#

open System

let res = (21) |> Seq.unfold (fun x -> Some(x,x+1)) |> Seq.filter (fun x ->
x % 11 = 0 & x % 12 = 0 & x % 13 = 0 & x % 14 = 0 & x % 15 = 0 & x % 16 = 0 & x % 17 = 0 & x % 18 = 0 & x % 19 = 0 & x % 20 = 0 ) |> Seq.head

printfn “Lowest LCM is %d” res Console.ReadLine()