The sum of the squares of the first ten natural numbers is,

1² + 2² + ... + 10² = 385

The square of the sum of the first ten natural numbers is,

(1 + 2 + ... + 10)² = 55² = 3025

Hence the difference between the sum of the squares of the first ten natural numbers and the square of the sum is 3025 − 385 = 2640.

Find the difference between the sum of the squares of the first one hundred natural numbers and the square of the sum.

This problem is easy in both C# and F#

F# 

let sum lst = List.fold_left (+) 0 lst

let sqr i = i * i

 

let sumofsquares = sum (List.map sqr [1..100])

 

let sumsquared = sqr ( sum [1..100])

 

printf "%i"  (sumsquared - sumofsquares)

C# 

class Program

{

    public static decimal sqr(int i)

    {

        return i * i;

    }

 

 

    static void Main(string[] args)

    {

        decimal sumofsquares = Enumerable.Range(1, 100).Sum(i => i * i);

        decimal sumsquared = sqr(Enumerable.Range(1, 100).Sum());

        Console.WriteLine(sumsquared - sumofsquares);

        Console.ReadLine();

 

    }

}
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