Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:206BA1of2 GHM

Order: 20

Horizontal side: 206 Vertical side: 206

Elements: 3√2, 6, 6√2, 8√2, 12, 13, 16, 12√2, 24, 29, 21√2, 29√2, 45, 58, 74, 66√2, 103, 74√2, 132, 103√2.

Code: 1325 0 74 1034 103 103 1033 206 103 294 132 74 293 161 74 212 182 82 451 206 103 126 170 70 245 182 58 745 0 0 744 74 0 86 140 66 165 148 58 131 161 74 66 164 64 125 170 58 660 140 66 36 161 61 65 164 58 581 206 58

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)