Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:368AQ GHM

Order: 20

Horizontal side: 368 Vertical side: 368

Elements: 16√2, 32, 32√2, 33√2, 56, 64, 46√2, 66, 64√2, 92, 69√2, 102, 112, 82√2, 128, 92√2, 138, 128√2, 184, 184√2.

Code: 1845 0 184 1844 184 184 1286 240 240 563 240 184 1285 240 112 922 92 92 1381 138 184 692 207 115 1021 240 184 330 207 115 645 240 48 644 304 48 1123 368 0 923 92 0 462 138 46 820 174 82 661 240 82 325 240 16 324 272 16 164 256 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)