Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:112BA GHM

Order: 20

Horizontal side: 112 Vertical side: 112

Elements: 7, 6√2, 7√2, 8√2, 14, 16, 12√2, 21, 16√2, 24, 18√2, 21√2, 32, 24√2, 36, 30√2, 32√2, 35√2, 70, 56√2.

Code: 705 0 42 564 56 56 326 80 80 166 64 64 325 80 48 86 56 56 165 64 48 64 70 42 186 58 30 367 76 48 246 88 24 212 21 21 354 35 7 300 58 30 126 76 12 245 88 0 213 21 0 145 21 7 75 21 0 74 28 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)