Primitive Perfect Isosceles Right Triangled Square

Title: _r 18:184AI2of4 GHM

Order: 18

Horizontal side: 184 Vertical side: 184

Elements: 8√2, 10√2, 16, 20, 20√2, 30, 23√2, 40, 30√2, 46, 38√2, 60, 62, 46√2, 76, 69√2, 108, 92√2.

Code: 1087 0 184 386 70 146 767 108 184 926 92 92 603 70 86 302 100 116 80 100 116 623 92 46 167 92 108 232 115 69 106 0 76 207 10 86 206 10 66 407 30 86 305 0 46 690 115 69 465 0 0 464 46 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)