Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:234BO GHM

Order: 20

Horizontal side: 234 Vertical side: 234

Elements: 8, 8√2, 14, 16, 12√2, 24, 25, 24√2, 25√2, 36, 39, 32√2, 56, 64, 78, 92, 78√2, 85√2, 156, 117√2.

Code: 1565 0 78 1174 117 117 856 149 149 320 149 149 391 156 117 257 156 117 250 181 117 147 156 92 923 170 0 367 170 92 120 206 92 240 194 80 241 218 80 165 218 64 785 0 0 784 78 0 85 218 56 84 226 56 643 234 0 567 170 56

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)