The Problem

Compute 2¹⁰⁰⁰ and sum its digits.

The Solution

Like Problem 13, this problem is trivially easy because of .NET's BigInteger data type.

(pown 2I 1000).ToString()
|> Seq.map (fun c -> int32(c) - int32('0'))
|> Seq.sum

The pown function returns 2¹⁰⁰⁰ as a BigInteger. (Suffixing a numeric literal with I means it is a BigInteger literal)

Strings can be treated as Seq<char> and that's what we do here. We convert each digit into an integer and then finally sum the result.

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