16 lines
641 B
Plaintext
16 lines
641 B
Plaintext
defmodule Prime do
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def decomposition(n), do: decomposition(n, 2, [])
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defp decomposition(n, k, acc) when n < k*k, do: Enum.reverse(acc, [n])
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defp decomposition(n, k, acc) when rem(n, k) == 0, do: decomposition(div(n, k), k, [k | acc])
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defp decomposition(n, k, acc), do: decomposition(n, k+1, acc)
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end
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prime = Stream.iterate(2, &(&1+1)) |>
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Stream.filter(fn n-> length(Prime.decomposition(n)) == 1 end) |>
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Enum.take(17)
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mersenne = Enum.map(prime, fn n -> {n, round(:math.pow(2,n)) - 1} end)
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Enum.each(mersenne, fn {n,m} ->
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:io.format "~3s :~20w = ~s~n", ["M#{n}", m, Prime.decomposition(m) |> Enum.join(" x ")]
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end)
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