Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:50AF GHM

Order: 20

Horizontal side: 50 Vertical side: 50

Elements: 1, 1√2, 2, 2√2, 3√2, 5, 7, 5√2, 8, 7√2, 8√2, 13, 10√2, 16, 21, 16√2, 24, 26, 29, 21√2.

Code: 295 0 21 241 24 50 102 34 40 261 50 50 76 27 33 162 50 24 36 24 30 75 27 26 22 26 28 23 26 26 12 27 27 13 27 26 54 29 21 53 34 21 163 50 8 217 0 21 210 21 21 131 34 21 84 42 0 83 50 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)