nag_log_beta (s14cbc) Example Program Results
  a     b     ln(beta(a,b))
 0.20  1.00    1.6094e+00
 0.60  1.00    5.1083e-01
 1.00  0.20    1.6094e+00
 1.00  1.00    0.0000e+00
 2.00  2.00   -1.7918e+00
 5.00  5.00   -6.4457e+00
 6.00  2.00   -3.7377e+00
 6.00  3.00   -5.1240e+00