perl /home/lanx/perl/pm/integer-gap.pl
8
8
**** Mode: 0
Problem at 1.84467440737096e+19 = 2**64
  18446744073709551615   18446744073709551615   18446744073709551615
**** Mode: 1
Problem at 9.00719925474099e+15 = 2**53
      9007199254740991       9007199254740992       9007199254740993
**** Mode: 2
Problem at 4.61168601842739e+18 = 2**62
   4611686018427387904    4611686018427387904    4611686018427387904