Program.cs

Program.cs

using System;

class Program
{
    static void Main()
    {
        for (int i = 1; i <= int.MaxValue; i++)
        {
            bool result = isEven(i);
            Console.WriteLine($"Number: {i}, Is Even: {result}");
        }
    }

    static bool isEven(int number)
    {
        var fibonacci = GenerateFibonacci();
        int positionInFibonacci = fibonacci.IndexOf(number);
        bool isPrime = IsPrime(number);
        char charRepresentation = (char)(number + '0');
        bool isAsciiEven = charRepresentation % 2 == 0;

        return (positionInFibonacci >= 0 && positionInFibonacci % 2 == 0) || (!isPrime && isAsciiEven);
    }

/* Yes we generate a full sequence for every call to is even */
static List<int> GenerateFibonacci()
{
    var fibonacci = new List<int> { 0, 1 };

    try 
    {
        while (true)
        {
            int next = checked(fibonacci[fibonacci.Count - 1] + fibonacci[fibonacci.Count - 2]);
            fibonacci.Add(next);
        }
    }
    catch (OverflowException)
    {
        // When overflow occurs, just stop adding to the list.
    }

    return fibonacci;
}

    static bool IsPrime(int number)
    {
        if (number < 2) return false;
        for (int i = 2; i <= Math.Sqrt(number); i++)
        {
            if (number % i == 0) return false;
        }
        return true;
    }
}