Primitive Perfect Isosceles Right Triangled Square

Title: _r 18:94AF3of4 GHM

Order: 18

Horizontal side: 94 Vertical side: 94

Elements: 5, 6, 6√2, 7√2, 12, 14, 12√2, 18, 19, 14√2, 24, 19√2, 28, 28√2, 42, 52, 40√2, 47√2.

Code: 527 0 94 280 52 94 281 80 94 142 94 80 141 94 94 406 54 40 243 24 42 122 36 54 181 42 66 195 42 47 194 61 47 123 36 42 62 42 48 63 42 42 57 42 47 470 47 47 74 54 40 427 0 42

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)