[B'] R = 2.00000: fails at (753.985, 754.485)   (151 s)
   [B'] R = 1.50000: closes   (222 s)
   [B'] R = 1.75000: fails at (753.985, 754.485)   (281 s)
   [B'] R = 1.62500: closes   (368 s)
   [B'] R = 1.68750: closes   (437 s)
   [B'] R = 1.71875: closes   (509 s)
   [B'] R = 1.73438: closes   (583 s)
   [B'] R = 1.74219: fails at (753.985, 754.485)   (642 s)
   [B'] R = 1.73828: fails at (753.985, 754.485)   (707 s)
   [B'] R = 1.73633: closes   (779 s)
   [B'] R = 1.73730: closes   (861 s)
   [B'] R = 1.73779: fails at (753.985, 754.485)   (932 s)
[B'] zero-free region beta <= 1 - 1/(R log|gamma|) for |gamma| > 3e12 with R <= 1.73730 suffices; fails at 1.73779   (932 s)