Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:125AD GHM

Order: 20

Horizontal side: 125 Vertical side: 125

Elements: 9, 12√2, 18, 22, 24, 18√2, 26, 27, 20√2, 31, 24√2, 25√2, 36, 27√2, 40, 45, 50, 40√2, 49√2, 80.

Code: 807 0 125 503 80 75 252 105 100 451 125 125 200 105 100 313 85 49 407 85 80 406 85 40 126 18 63 247 30 75 246 30 51 267 54 75 186 0 45 365 18 27 227 54 49 490 76 49 91 85 49 185 0 27 275 0 0 274 27 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)