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 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);
}
}
}
}