Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:225AD GHM

Order: 20

Horizontal side: 225 Vertical side: 225

Elements: 3, 9, 11, 12, 9√2, 15, 11√2, 12√2, 18, 15√2, 22, 53, 53√2, 75, 86, 97, 75√2, 86√2, 139, 150.

Code: 1505 0 75 1391 139 225 867 139 225 866 139 139 152 154 124 153 154 109 185 154 106 127 139 109 120 151 109 31 154 109 94 163 97 93 172 97 532 225 53 117 139 97 116 139 86 227 150 97 973 172 0 755 0 0 754 75 0 533 225 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)