Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:126AQ4of4 GHM

Order: 20

Horizontal side: 126 Vertical side: 126

Elements: 8√2, 9√2, 14, 16, 18, 14√2, 16√2, 24, 18√2, 28, 20√2, 24√2, 27√2, 28√2, 42, 48, 36√2, 56, 70, 90.

Code: 905 0 36 561 56 126 425 56 84 701 126 126 147 56 84 146 56 70 287 70 84 280 98 84 204 90 36 86 102 48 167 110 56 166 110 40 483 102 0 242 126 24 182 18 18 181 18 36 92 27 27 364 54 0 270 27 27 243 126 0

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)