Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:216AB1of2 GHM

Order: 20

Horizontal side: 216 Vertical side: 216

Elements: 4√2, 8, 8√2, 12√2, 20, 24, 20√2, 24√2, 27√2, 34√2, 37√2, 54, 40√2, 74, 54√2, 88, 71√2, 108, 81√2, 108√2.

Code: 1082 108 108 814 81 135 540 162 216 541 216 216 276 81 135 1087 108 162 883 216 74 376 71 71 206 108 54 82 136 66 81 136 74 42 140 70 404 176 34 743 216 0 710 71 71 120 140 70 247 128 58 240 152 58 205 108 34 344 142 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)