public void TestPentagonalNthNumber()
{
var expected = 40755;
var actual = PentagonalNumberGenerator.NthNumber(165);
Assert.AreEqual(expected, actual);
}
static void Main(string[] args)
{
// all hexagonal numbers are also triangle numbers
// only need to find next hexagonal number which is also
// a pentagonal number
int p = 166;
int h = 144;
BigInteger pNum = PentagonalNumberGenerator.NthNumber(p);
BigInteger hNum = HexagonalNumberGenerator.NthNumber(h);
while (pNum != hNum && pNum > 0)
{
if (pNum < hNum)
{
p++;
pNum = PentagonalNumberGenerator.NthNumber(p);
}
else
{
h++;
hNum = HexagonalNumberGenerator.NthNumber(h);
}
}
Console.WriteLine(hNum);
Console.ReadKey();
}
