static void CalculatePrimePhi()
{
for (int i = 2; i <= MAXINT; i++)
{
if (primes[i])
{
phiResult[i] = i - 1;
continue;
}
List <int> frac = fg.GeneratorFactorsBelowOneMillion(i);
var fracGroup = frac.GroupBy(x => x);
int count = fracGroup.Count();
if (count == 1)
{
phiResult[i] = EulerTotientFunction.Calculate(i);
continue;
}
phiResult[i] = 1;
foreach (var item in fracGroup)
{
int num = item.First();
int itemcount = item.Count();
int sumNum = (int)Math.Pow(num, itemcount);
phiResult[i] *= phiResult[sumNum];
}
}
}
static int Phi(int num)
{
if (phiResult[num] != 0)
{
return(phiResult[num]);
}
return(EulerTotientFunction.Calculate(num));
}
