using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        List<decimal> numbers = new List<decimal> { 2, 3, 5, 8, 13 };

        int windowSize = 3;

        var movingAverages = numbers

        .Select((number, index) => new

        {

            Number = number,

            Index = index

        })

        .Select(n => new

        {

            n.Number,

            Average = numbers

                .Skip(Math.Max(0, n.Index - windowSize + 1))

                .Take(windowSize)

                .Average()

        })

        .ToList();

​

        foreach (var item in movingAverages)

        {

            Console.WriteLine($"Number: {item.Number}, Moving Average: {item.Average}");

        }

​

​

    }

}