Primitive Perfect Isosceles Right Triangled Square

Title: _d 18:182AA GHM

Order: 18

Horizontal side: 182 Vertical side: 182

Elements: 1√2, 2, 2√2, 4, 4√2, 8, 8√2, 15√2, 30, 30√2, 46, 60, 61, 76, 91, 106, 76√2, 91√2.

Code: 1065 0 76 914 91 91 913 182 91 154 106 76 10 121 91 611 182 91 20 120 90 21 122 90 605 122 30 40 118 88 41 122 88 80 114 84 81 122 84 767 0 76 760 76 76 461 122 76 304 152 0 303 182 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)