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Problem
The series, 11 + 22 + 33 + … + 1010 = 10405071317.
Find the last ten digits of the series, 11 + 22 + 33 + … + 10001000.
Solution
let number = [1..1000] |> List.map (fun n -> pown (bigint(n)) n) |> List.sum
let answer =
number.ToString().ToCharArray()
|> Array.rev
|> Seq.take 10
|> Seq.toArray
|> Array.rev
