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);
}
private static int PandigitalHigherPrime(int missing, int number)
{
if (missing == 0)
{
if (PrimeNumbers.IsPrimeNumber(number))
{
return(number);
}
return(-1);
}
var aux = missing;
var div = 10;
var antDiv = 1;
while (aux > 0)
{
var nextMissing = missing / div * antDiv + missing % antDiv;
var nextNumber = number * 10 + aux % 10;
var result = PandigitalHigherPrime(nextMissing, nextNumber);
if (result > -1)
{
return(result);
}
aux /= 10;
antDiv = div;
div *= 10;
}
return(-1);
}
public static long PrimePermutations()
{
var primesWith4Numbers = new List <(long num, int orderedNum)>();
for (int i = 1235; i <= 9875; i += 2)
{
if (PrimeNumbers.IsPrimeNumber(i))
{
primesWith4Numbers.Add((i, OrderedNum(i)));
}
}
for (int i = 0; i < primesWith4Numbers.Count; i++)
{
var(firstNum, firstOrderedNum) = primesWith4Numbers[i];
for (int j = i + 1; j < primesWith4Numbers.Count; j++)
{
if (firstOrderedNum == primesWith4Numbers[j].orderedNum)
{
var(secondNum, secondOrderedNum) = primesWith4Numbers[j];
var firstDiff = secondNum - firstNum;
for (int k = j + 1; k < primesWith4Numbers.Count; k++)
{
var(thirdNum, thirdOrderedNum) = primesWith4Numbers[k];
var lastDiff = thirdNum - secondNum;
if (lastDiff > firstDiff)
{
break;
}
if (lastDiff == firstDiff && thirdOrderedNum == firstOrderedNum)
{
var joinedNumbers = firstNum.JoinWith(secondNum.JoinWith(thirdNum));
if (joinedNumbers != 148748178147)
{
return(joinedNumbers);
}
}
}
}
}
}
return(0);
}