static void Main(string[] args)
{
int max = 10000;
int[] factorsSum = new int[max - 1];
for (int i = 0; i < factorsSum.Length; i++)
{
SortedSet <int> tempFactors = ExtraNumbers.Factors(i + 2);
for (int j = 0; j < tempFactors.Count - 1; j++)
{
factorsSum[i] += tempFactors.ElementAt(j);
}
}
int amicablesum = 0;
for (int i = 0; i < factorsSum.Length; i++)
{
if (1 < factorsSum[i] && factorsSum[i] < max - 2)
{
if (i + 2 == factorsSum[factorsSum[i] - 2] && factorsSum[i] != i + 2)
{
amicablesum += i + 2;
}
}
}
Console.WriteLine(amicablesum);
Console.ReadLine();
}
static int DigitFactorialSum(int n)
{
int sum = 0;
while (n > 0)
{
sum += (int)ExtraNumbers.Factorial(n % 10);
n /= 10;
}
return(sum);
}
private static int LengthPrimes(int i, int j)
{
int counter = 0;
while (ExtraNumbers.IsPrime(counter * counter + i * counter + j))
{
counter++;
}
return(counter);
}
private static bool ConsecutiveFactors(int start, int noFactors)
{
for (int i = 0; i < noFactors; i++)
{
if (ExtraNumbers.PrimeFactors(start + i).Distinct().Count() != noFactors)
{
return(false);
}
}
return(true);
}
static bool IsAbundant(int number)
{
SortedSet <int> factors = ExtraNumbers.Factors(number);
int sum = 0;
for (int i = 0; i < factors.Count - 1; i++)
{
sum += factors.ElementAt(i);
}
return(sum > number);
}
static void Main(string[] args)
{
List <string> permutations = ExtraNumbers.AllPermutations("7654321");
foreach (string s in permutations)
{
if (ExtraNumbers.IsPrime(int.Parse(s)))
{
Console.WriteLine(s);
break;
}
}
Console.ReadLine();
}
static void Main(string[] args)
{
long sum = 0;
List <string> permutations = ExtraNumbers.AllPermutations("0123456789");
foreach (string s in permutations)
{
if (Divisibilities(s))
{
sum += long.Parse(s);
}
}
Console.WriteLine(sum);
Console.ReadLine();
}
private static bool IsPandigitalProducts(int n)
{
SortedSet <int> factors = ExtraNumbers.Factors(n);
for (int i = 0; i < factors.Count / 2; i++)
{
int product1 = factors.ElementAt(i);
int product2 = factors.ElementAt(factors.Count - 1 - i);
if (IsAllPandigital(n, product1, product2))
{
return(true);
}
}
return(false);
}
static void Main(string[] args)
{
int numberOfFactors = 500;
int foundFactors = 1;
int counter = 1;
int triangle = 1;
while (foundFactors <= numberOfFactors)
{
triangle = TriangleAt(counter);
foundFactors = ExtraNumbers.Factors(triangle).Count;
counter++;
}
Console.WriteLine(triangle);
Console.Read();
}
static void Main(string[] args)
{
int max = 2000000;
bool[] primes = ExtraNumbers.Sieve(max);
BigInteger sum = 0;
for (int i = 0; i < primes.Length; i++)
{
if (!primes[i])
{
sum += i + 2;
}
}
Console.WriteLine(sum);
Console.Read();
}
