Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:177AC GHM

Order: 20

Horizontal side: 177 Vertical side: 177

Elements: 14, 11√2, 12√2, 22, 24, 22√2, 33, 26√2, 43, 44, 48, 52, 43√2, 66, 67, 48√2, 77, 86, 67√2, 96.

Code: 675 0 110 674 67 110 430 134 177 431 177 177 243 91 110 122 103 122 861 177 134 260 103 122 777 0 110 663 77 44 147 77 110 527 77 96 963 129 0 482 177 48 483 177 0 116 0 33 227 11 44 226 11 22 447 33 44 335 0 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)