Summary: The authors continue their series on number patterns considering a number staircase in a 100-square ‒ first meeting with the divisibility. This is the third in a series of exploring number patterns in arrays of numbers. The authors document their work in a consistent format throughout the series, and offer suggestions for extending the ideas for different groups of learners. Pattern spotting is a useful tool for pupils developing their mathematics through the world of number. Some learners are fascinated by number patterns, others motivated by the challenge to seek in the same array of numbers. Some of the ideas developed here have their roots in the earlier articles, so trying the tasks yourself prior to using in the classroom is advised. For the first two parts see [the authors, ibid. 231, 9‒14 (2012; ME 2013d.00373); ibid. 232, 9‒12 (2013; ME 2015f.00558)].