Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:263AA4of4 GHM

Order: 20

Horizontal side: 263 Vertical side: 263

Elements: 12, 12√2, 24, 26, 29, 24√2, 36, 26√2, 36√2, 52, 42√2, 52√2, 78, 65√2, 104, 107, 78√2, 130, 133, 185.

Code: 1857 0 263 1333 185 130 787 185 263 786 185 185 365 185 149 242 209 125 241 209 149 122 221 137 121 221 149 422 263 107 366 185 101 526 0 78 1047 52 130 1303 156 0 652 221 65 291 185 130 1073 263 0 525 0 26 265 0 0 264 26 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)