Exemplo n.º 1
0
        public static int ProductOfCoefficientOfQuadraticFormulaProducingMorePrimeNumbers()
        {
            var maxPrimeNumbers = int.MinValue;
            int aValue          = int.MinValue;
            int bValue          = int.MinValue;
            var primesUntil999  = PrimeNumbers.PrimesUntilN(999);

            for (int a = -999; a < 1000; a++)
            {
                for (int b = 2; b <= 999; b++)
                {
                    if (primesUntil999[b])
                    {
                        int n;

                        for (n = 1; PrimeNumbers.IsPrimeNumber(n * n + a * n + b); n++)
                        {
                            ;
                        }

                        if (n > maxPrimeNumbers)
                        {
                            maxPrimeNumbers = n;
                            aValue          = a;
                            bValue          = b;
                        }
                    }
                }
            }

            return(aValue * bValue);
        }
Exemplo n.º 2
0
        public static long SumPrimesBelowN(int num)
        {
            var  primes = PrimeNumbers.PrimesUntilN(num - 1);
            long sum    = 2;

            for (int i = 3; i < primes.Length; i += 2)
            {
                if (primes[i])
                {
                    sum += i;
                }
            }

            return(sum);
        }
Exemplo n.º 3
0
        public static int ConsecutivePrimeSum(int num)
        {
            var primes           = PrimeNumbers.PrimesUntilN(num);
            int greatestPrimeSum = 0;
            int largestStreak    = 0;

            for (int i = 0; i < primes.Length; i++)
            {
                if (primes[i])
                {
                    int currentStreak = 0;
                    int currentSum    = 0;

                    for (int j = i; j < primes.Length; j++)
                    {
                        if (primes[j])
                        {
                            currentSum += j;

                            if (currentSum >= num)
                            {
                                break;
                            }

                            currentStreak++;

                            if (primes[currentSum] && currentStreak > largestStreak)
                            {
                                largestStreak    = currentStreak;
                                greatestPrimeSum = currentSum;
                            }
                        }
                    }
                }
            }

            return(greatestPrimeSum);
        }
 public E035_Circular_primes(int threshold)
 {
     _threshold    = threshold;
     _primeNumbers = PrimeNumbers.PrimesUntilN(_threshold - 1);
 }