Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:328AT GHM

Order: 20

Horizontal side: 328 Vertical side: 328

Elements: 2, 2√2, 4, 4√2, 19√2, 28, 20√2, 22√2, 24√2, 28√2, 56, 42√2, 80, 84, 122, 103√2, 164, 122√2, 206, 164√2.

Code: 2065 0 122 1644 164 164 1643 328 164 424 206 122 226 226 142 242 272 140 801 328 164 200 226 142 286 244 112 565 272 84 1225 0 0 1224 122 0 196 225 103 27 244 122 20 246 122 42 248 116 41 248 120 285 244 84 1030 225 103 841 328 84

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)