Primitive Perfect Isosceles Right Triangled Square

Title: _d 19:124BK1of4 GHM

Order: 19

Horizontal side: 124 Vertical side: 124

Elements: 1√2, 5, 5√2, 10, 8√2, 9√2, 10√2, 15, 16, 18, 20, 18√2, 36, 44, 53, 62, 71, 53√2, 62√2.

Code: 715 0 53 624 62 62 623 124 62 94 71 53 80 80 62 441 124 62 10 72 54 161 88 54 365 88 18 537 0 53 530 53 53 104 63 43 103 73 43 155 73 38 54 68 38 53 73 38 201 88 38 184 106 0 183 124 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)