public static IEnumerable <int> GetProperDivisors(this int n)
{
FactorizedNumber factorized = n.Factorize();
var results = new List <int>();
void Loop(FactorizedNumber number, int factorIndex, int currentResult)
{
int prime = number[factorIndex].Prime;
for (int e = 0; e <= number[factorIndex].Exponent; e++)
{
if (e > 0)
{
currentResult *= prime;
}
if (factorIndex == number.Count - 1)
{
results.Add(currentResult);
}
else
{
Loop(number, factorIndex + 1, currentResult);
}
}
}
Loop(factorized, 0, 1);
return(results.Where(x => x != n));
}
public static int GetEulersTotient(this int n)
{
FactorizedNumber factorizedNumber = n.Factorize();
BigInteger result = 1;
foreach (PrimeFactor primeFactor in factorizedNumber)
{
BigInteger p2 = BigInteger.Pow(primeFactor.Prime, primeFactor.Exponent - 1);
BigInteger p1 = p2 * primeFactor.Prime;
result *= p1 - p2;
}
return((int)result);
}
