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- Function:
*double***gsl_sf_poch***(double*`a`, double`x`) - Function:
*int***gsl_sf_poch_e***(double*`a`, double`x`, gsl_sf_result *`result`) -
These routines compute the Pochhammer symbol

*(a)_x = \Gamma(a + x)/\Gamma(a)*. The Pochhammer symbol is also known as the Apell symbol and sometimes written as*(a,x)*. When*a*and*a+x*are negative integers or zero, the limiting value of the ratio is returned.

- Function:
*double***gsl_sf_lnpoch***(double*`a`, double`x`) - Function:
*int***gsl_sf_lnpoch_e***(double*`a`, double`x`, gsl_sf_result *`result`) -
These routines compute the logarithm of the Pochhammer symbol,

*\log((a)_x) = \log(\Gamma(a + x)/\Gamma(a))*.

- Function:
*int***gsl_sf_lnpoch_sgn_e***(double*`a`, double`x`, gsl_sf_result *`result`, double *`sgn`) These routines compute the sign of the Pochhammer symbol and the logarithm of its magnitude. The computed parameters are

*result = \log(|(a)_x|)*with a corresponding error term, and*sgn = \sgn((a)_x)*where*(a)_x = \Gamma(a + x)/\Gamma(a)*.

- Function:
*double***gsl_sf_pochrel***(double*`a`, double`x`) - Function:
*int***gsl_sf_pochrel_e***(double*`a`, double`x`, gsl_sf_result *`result`) -
These routines compute the relative Pochhammer symbol

*((a)_x - 1)/x*where*(a)_x = \Gamma(a + x)/\Gamma(a)*.