public static long TriangularPentagonalHexagonal()
{
var h = 144;
long hexagonal;
do
{
hexagonal = TriPenHexNumbers.HexagonalNumber(h++);
} while (!(TriPenHexNumbers.IsPentagonNumber(hexagonal) &&
TriPenHexNumbers.IsTriangleNumber(hexagonal)));
return(hexagonal);
}
public static long FirstTriangleNumberWithOverFiveHundredDivisors()
{
var pointReached = false;
long number = -1;
for (int i = 1; !pointReached; i += 2)
{
number = TriPenHexNumbers.TriangleNumber(i);
if (HasMoreThan500Divisors(number))
{
pointReached = true;
}
}
return(number);
}
public static long MinimisedPentagonalNumbersDifference()
{
for (int k = 2; true; k++)
{
var kPentagon = TriPenHexNumbers.PentagonNumber(k);
for (int j = k - 1; j >= 1; j--)
{
var jPentagon = TriPenHexNumbers.PentagonNumber(j);
var diff = kPentagon - jPentagon;
if (TriPenHexNumbers.IsPentagonNumber(diff) && TriPenHexNumbers.IsPentagonNumber(kPentagon + jPentagon))
{
return(diff);
}
}
}
}
public static int NumTriangleWords()
{
var triangleNumbers = new List <int> {
1
};
var numTriangleWords = 0;
foreach (var word in _words)
{
var wordNumber = word.Select(w => _dictionary[w]).Sum();
if (TriPenHexNumbers.IsTriangleNumber(wordNumber))
{
numTriangleWords++;
}
}
return(numTriangleWords);
}
