I must compute value of 1-regularized incomplete gamma function (upper) $Q(a,z)$.
But unfortunatelly this computing exceeding the precision of the processor (for example I gain 0, but I should have 0.000000000000001).
To resolve this problem I want to use logarithm of $(1 - Q(a,z))$.
How I can compute this $\log(1 - Q(a,z))$ formula using series expansion. Is there any formula for this expansion?
Thanks a lot for help