For integer parameters greater than 6, tgamma(n+1) != n!
(note: 719 and beyond are off-by-one, while the real parameter at the bottom results in 720)

#include <iostream>
#include <cmath>
using namespace std;
int main(void)
{
	uint64_t foo;
	for(int i=0; i < 10; i++)
	{
		foo = tgamma(i);
		cout << foo << "\n";
	}
	cout << tgamma(7.0) << "\n";
}

0
1
1
2
6
24
120
719
5039
40319
720