the first parameter is the cumulative sum of the sequence,

  >>> log(1002, 10)
  3.0008677215312267
  >>> log(634, 9)
  2.936454025222717
  >>> log(409, 8)
  2.89198567764725
  >>> log(275, 7)
  2.8864493565611764
  >>> log(186, 6)
  2.9165447502641713
  >>> log(108, 5)
  2.9091716996047423
  >>> log(61, 4)
  2.9653686687814433
  >>> log(39, 3)
  3.3347175194727923
  >>> log(18, 2)
  4.169925001442312

yes, I saw that "read more" at first...I did not want to spoil the puzzle so I tried to solve it on my own for a while but then realized I might have to spend more than 1 hour on this thing -- and at this point I totally forgot there is a spoiler there...