Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:168AN4of4 GHM

Order: 20

Horizontal side: 168 Vertical side: 168

Elements: 8, 6√2, 8√2, 12, 12√2, 13√2, 24, 18√2, 26, 21√2, 24√2, 34, 42, 42√2, 68, 50√2, 76, 84, 92, 84√2.

Code: 927 0 168 683 92 100 767 92 168 846 84 84 243 24 76 122 36 88 121 36 100 62 42 94 244 60 76 506 34 50 82 92 92 81 92 100 180 42 94 845 84 0 347 0 76 136 21 63 267 34 76 210 21 63 427 0 42 420 42 42

The properties below may precede order:side in a tiling's title:

• c = crossed. There is a tile-corner traversed by two lines. The only known crossed PPIRTS's below order 20 are 19:35AB1of4 and 19:35AB4of4.
• d = double-pentagon patterned. Every such tiling is a subdivision of an instance of the same deformable tiling by two 45-90-90-90-225 pentagons with a shared side, four triangles and two pseudotriangles. All below order 19 are degenerate in the sense that one or more sides of underlying tiles have shrunk to zero length. The non-degenerate d-tilings of order 19 are 19:221AA, 19:229AB and 19:241AA.
• e = elegant. No tile-corner is just a T-junction. Such tilings may be considered aesthetically pleasing. The only known elegant PPIRTS's below order 16 are 13:21AA, 14:26AJ, 14:35AA and 15:55AA.
• i = isomers exist which are ineligible for this catalogue. They are not included in the isomer count which follows 'of' in the tiling id.
• r = rectangular inclusion. The only known PPIRTS's below order 16 with a rectangular inclusion are 13:18AA1-4of4 and 15:44AA1-4of4.

Credit for Discovery

Just three people are credited with the discovery of Primitive Perfects:

Geoffrey H. Morley (GHM, England)

Jasper D. Skinner, II (JDS, United States)

William T. Tutte (WTT, Canada, 1917-2002) (15:44AI, 17:136AJ and 19:56AJ only)