Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:89AE GHM

Order: 20

Horizontal side: 89 Vertical side: 89

Elements: 7√2, 12, 13, 14, 12√2, 13√2, 20, 16√2, 24, 25, 26, 28, 20√2, 24√2, 25√2, 36, 37, 39, 40, 32√2.

Code: 395 0 50 324 32 57 250 64 89 251 89 89 76 32 57 147 39 64 403 53 24 202 73 44 361 89 64 137 0 50 136 0 37 267 13 50 203 73 24 162 89 28 375 0 0 283 89 0 244 37 0 243 61 0 122 73 12 121 73 24

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)