Sixteen set of increasing density of equidistant vertical lines [Seize ensembles de densité croissante de droites verticales équidistantes].
--------- | 03 | 04 | |----+----| | 01 | 02 | ---------
------------------- | 13 | 14 | 15 | 16 | |----+----+----+----| | 09 | 10 | 11 | 12 | |----+----+----+----| | 05 | 06 | 07 | 08 | |----+----+----+----| | 01 | 02 | 03 | 04 | -------------------
--------------------------------------- | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | |----+----+----+----+----+----+----+----| | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | |----+----+----+----+----+----+----+----| | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | |----+----+----+----+----+----+----+----| | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | |----+----+----+----+----+----+----+----| | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | |----+----+----+----+----+----+----+----| | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | |----+----+----+----+----+----+----+----| | 09 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | |----+----+----+----+----+----+----+----| | 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | ---------------------------------------respectively for 2x2, 4x4 and 8x8 pictures.