minimum = 3, maximum = 11, so loop from 3 to 7
first interval is 3-7, so includes 3,4,6,7
  process 3 & 4
  process 3 & 6
  process 3 & 7
  process 4 & 6
  process 4 & 7
  process 6 & 7
next interval is 4-8, so includes 4,6,7,8
  skip 4 & 6, already done
  skip 4 & 7, already done
  process 4 & 8
  skip 6 & 7, already done
  process 6 & 8
  process 7 & 8
next interval is 5-9, so includes 6,7,8
  skip 6 & 7, already done
  skip 6 & 8, already done
  skip 7 & 8, already done
next interval is 6-10, so includes 6,7,8
  skip 6 & 7, already done
  skip 6 & 8, already done
  skip 7 & 8, already done
next interval is 7-11, so includes 7,8,11
  skip 7 & 8, already done
  process 7 & 11
  process 8 & 11