Primitive Perfect Isosceles Right Triangled Square

Title: _d 18:106AI GHM

Order: 18

Horizontal side: 106 Vertical side: 106

Elements: 2√2, 4, 4√2, 8, 11, 10√2, 11√2, 18, 14√2, 20, 20√2, 29, 33, 43, 53, 43√2, 63, 53√2.

Code: 635 0 43 534 53 53 533 106 53 104 63 43 20 73 53 331 106 53 83 71 43 42 75 47 41 75 51 112 86 40 183 75 29 437 0 43 430 43 43 144 57 29 113 86 29 202 106 20 291 86 29 203 106 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)