Problems with GAMMA functions?

[Jerry DeLisle]

Heres some test data.  Its failing in the do loop for two values at n=18 and 19:

  n   xs             ts              abs(gamma(xs)-ts)/ts

  1   1.5000000      0.88622695       0.0000000
  2   2.5000000       1.3293403       0.0000000
  3   3.5000000       3.3233509      7.17404163E-08
  4   4.5000000       11.631728      2.45967129E-07
  5   5.5000000       52.342777      2.18637453E-07
  6   6.5000000       287.88528      2.12012068E-07
  7   7.5000000       1871.2543       0.0000000
  8   8.5000000       14034.407      4.17500701E-07
  9   9.5000000       119292.46      4.58432169E-07
10   10.500000       1133278.4      8.82395739E-07
11   11.500000       11899423.      1.26056534E-06
12   12.500000      1.36843360E+08  8.18454055E-07
13   13.500000      1.71054208E+09  3.74150403E-07
14   14.500000      2.30923182E+10  1.50768756E-06
15   15.500000      3.34838596E+11  1.56579324E-06
16   16.500000      5.18999822E+12  1.31324589E-06
17   17.500000      8.56349706E+13  8.81619656E-07
18   18.500000      1.49861207E+15  2.14947249E-06
19   19.500000      2.77243231E+16  2.55612940E-06
20   20.500000      5.40624301E+17   0.0000000

Regards,

Jerry