Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:242AD GHM

Order: 20

Horizontal side: 242 Vertical side: 242

Elements: 11√2, 16, 16√2, 32, 26√2, 48, 52, 55, 48√2, 74, 77, 55√2, 80, 58√2, 88, 96, 77√2, 110, 84√2, 88√2.

Code: 1105 0 132 844 84 158 580 168 242 741 242 242 266 84 158 527 110 184 963 162 88 482 210 136 481 210 184 167 210 184 160 226 184 327 210 168 803 242 88 555 0 77 554 55 77 110 66 88 884 154 0 883 242 0 777 0 77 770 77 77

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)