Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:204AJ1of4 GHM

Order: 20

Horizontal side: 204 Vertical side: 204

Elements: 2, 2√2, 4, 4√2, 6, 5√2, 8, 10, 28, 28√2, 32√2, 46, 56, 42√2, 51√2, 74, 102, 74√2, 130, 102√2.

Code: 1305 0 74 1024 102 102 1023 204 102 284 130 74 283 158 74 467 158 102 516 153 51 747 0 74 740 74 74 424 116 32 46 154 70 63 154 64 45 154 66 25 154 64 24 156 64 103 158 56 326 116 32 87 148 64 565 148 0 54 153 51

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)