By defining the Beta Function in terms of the Gamma
Function,
$$B(a,b)=\frac{\Gamma(a)\Gamma(b)}{\Gamma(a+b)}$$
the function can be defined for non-integer negative values of
a and b. The special case of this where \(a=b\) is needed
to calculate the standard errors of the L Moment estimates of the
gpd type of the generalised lambda distribution, so this function
carries out that calculation.