Primitive Perfect Isosceles Right Triangled Square

Title: _d 18:184AD GHM

Order: 18

Horizontal side: 184 Vertical side: 184

Elements: 5√2, 10, 12, 10√2, 12√2, 18, 15√2, 24, 18√2, 24√2, 38, 48, 68, 80, 92, 104, 80√2, 92√2.

Code: 1045 0 80 924 92 92 923 184 92 124 104 80 123 116 80 152 131 77 681 184 92 807 0 80 800 80 80 184 98 62 183 116 62 50 131 77 100 126 72 101 136 72 485 136 24 381 136 62 244 160 0 243 184 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)