Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:272AV GHM

Order: 20

Horizontal side: 272 Vertical side: 272

Elements: 16, 16√2, 17√2, 28, 32, 46, 48, 34√2, 48√2, 68, 74, 80, 57√2, 62√2, 96, 68√2, 102, 96√2, 136, 136√2.

Code: 1365 0 136 1364 136 136 966 176 176 576 119 119 965 176 80 682 68 68 1021 102 136 745 102 62 174 119 119 485 176 32 484 224 32 803 272 0 683 68 0 342 102 34 287 102 62 620 130 62 461 176 62 167 176 32 166 176 16 327 192 32

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)