Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:147AA GHM

Order: 20

Horizontal side: 147 Vertical side: 147

Elements: 11, 24, 18√2, 21√2, 22√2, 24√2, 35, 25√2, 36, 40, 42, 44, 46, 48, 36√2, 59, 42√2, 44√2, 63, 63√2.

Code: 637 0 147 636 0 84 407 63 147 226 81 125 447 103 147 446 103 103 180 81 125 367 63 107 366 63 71 485 99 59 422 42 42 252 88 46 245 99 35 244 123 35 593 147 0 463 88 0 115 88 35 423 42 0 212 63 21 357 88 35

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)