Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:206BC2of2 GHM

Order: 20

Horizontal side: 206 Vertical side: 206

Elements: 4, 4√2, 6, 7, 8, 6√2, 7√2, 10, 8√2, 14, 37, 44, 44√2, 74, 81, 88, 74√2, 81√2, 125, 132.

Code: 1325 0 74 1251 125 206 817 125 206 816 125 125 375 125 88 77 125 88 76 125 81 147 132 88 60 146 88 61 152 88 107 152 88 883 162 0 442 206 44 80 140 82 81 148 82 42 152 78 41 152 82 745 0 0 744 74 0 443 206 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)