# factorial(n) is n!; #factorial(0,x_):=factorial(x); #factorial(1,x_):=factorial(x)*psi(x+1); #factorial(x_):=gamma(x+1); factorial(-3/2):= -2sqrt(pi); factorial(-1/2):= sqrt(pi); factorial(1/2):= sqrt(pi)/2; factorial(3/2):= 3/4*sqrt(pi);