Primitive Perfect Isosceles Right Triangled Square

Title: __ 18:136AK JDS

Order: 18

Horizontal side: 136 Vertical side: 136

Elements: 2√2, 10√2, 12√2, 13√2, 14√2, 20, 26, 28, 20√2, 26√2, 28√2, 40, 54, 56, 40√2, 41√2, 82, 68√2.

Code: 825 0 54 684 68 68 406 96 96 286 68 68 405 96 56 205 96 36 204 116 36 563 136 0 545 0 0 414 41 13 283 82 26 142 96 40 26 94 38 120 94 38 104 106 26 136 41 13 265 54 0 264 80 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)