# gamma(a,x) is incomplete big Gamma(a,x) from x to oo; # gamma(n,0,x) is small gamma(n,x) from 0 to x; # gamma(n,a,x) is small gamma(n,x) from a to x; # gamma(1/2,x_) := -sqrt(pi)*erf(sqrt(x)); # gamma(1/2,-x_) := -sqrt(pi)*i*erfi(sqrt(x)); # gamma(0,0) := inf; # gamma(0,x_) = -Ei(-x)=En(1,x); #Gamma(s_,a_,b_):=gamma(s,a)-gamma(s,b); #gamma(s_,a_,b_):=gamma(s,a)-gamma(s,b); gamma(s_,a_,a_) :=0; gamma(s_,0,b_):=gamma(s)-gamma(s,b); gamma(s_,a_,inf) := gamma(s,a); gamma(a_,0):= gamma(a); gamma(a_,inf):= 0; gamma(0,x_) := -Ei(-x); gamma(1,x_):= exp(-x); #gamma(1+x_):=x!; gamma(-0.5):= -2*sqrt(pi); gamma(0.5):= sqrt(pi); gamma(3/2):= sqrt(pi)/2; gamma(5/2):= 3/4*sqrt(pi); gamma(zero):= infinity; gamma(-zero):= -infinity;