Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:206AD2of2 GHM

Order: 20

Horizontal side: 206 Vertical side: 206

Elements: 13, 12√2, 16√2, 24, 18√2, 32, 24√2, 36, 29√2, 30√2, 45, 48, 58, 42√2, 45√2, 58√2, 90, 74√2, 116, 103√2.

Code: 1165 0 90 1034 103 103 746 132 132 290 132 132 131 116 103 457 116 103 450 161 103 905 0 0 481 48 90 242 72 66 361 84 90 182 102 72 321 116 90 300 102 72 243 72 42 122 84 54 164 132 42 580 148 58 581 206 58 424 90 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)