int amount;

ASK_INPUT:
Console.WriteLine("Enter how many numbers you want to compute:");
string input = Console.ReadLine();

if(!Int32.TryParse(input, out amount)){
    Console.WriteLine("Input Wasn't a Number!");
    goto ASK_INPUT;
}

// Declare Variables used for Calculation
System.Numerics.BigInteger themp;
System.Numerics.BigInteger a = 1;
System.Numerics.BigInteger b = 1;

for (int i = 1; i < amount + 1; i++)
{
    Console.WriteLine($"{i}: {a}\n");
    themp = a;
    a = a + b;
    b = themp;
}