Primitive Perfect Isosceles Right Triangled Square

Title: __ 18:62AG GHM

Order: 18

Horizontal side: 62 Vertical side: 62

Elements: 2, 2√2, 3, 3√2, 6, 5√2, 9, 10, 12, 10√2, 16, 12√2, 18, 28, 23√2, 34, 25√2, 31√2.

Code: 345 0 28 314 31 31 256 37 37 63 37 31 95 37 28 34 34 28 33 37 28 285 0 0 234 23 5 183 46 10 165 46 12 25 46 10 24 48 10 120 50 12 121 62 12 56 23 5 105 28 0 104 38 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)