Exponentiate (decimal) - unworking

// http://stackoverflow.com/a/466434/848344
public decimal powVappolinario(decimal x, decimal y)
{
    return DecimalExp(y * LogN(x));
}

public decimal Exponentiate(decimal a, decimal b)
{
    decimal total = a;
    for (int i = 1; i < b; i++) total = a*total;
    return total;
}

public int Factorial(int n)
{
    int j=1;
    for(int i=1;i<=n;i++){ j = j*i; }
    return j;
}

// Adjust this to modify the precision
public const int ITERATIONS = 27;
// power series

public decimal DecimalExp(decimal power)
{
    int iteration = ITERATIONS;
    decimal result = 1;
    while (iteration > 0)
    {
        decimal fatorial = Factorial(iteration);
        result += Exponentiate(power, iteration) / fatorial;
        iteration--;
    }
    return result;
}

// natural logarithm series
public decimal LogN(decimal number)
{
    decimal aux = (number - 1);
    decimal result = 0;
    int iteration = ITERATIONS;
    while (iteration > 0)
    {
        result += Exponentiate(aux, iteration) / iteration;
        iteration--;
    }
    return result;
}