Primitive Perfect Isosceles Right Triangled Square

Title: _d 19:222AB GHM

Order: 19

Horizontal side: 222 Vertical side: 222

Elements: 4, 5√2, 10, 10√2, 20, 26, 30, 24√2, 35, 26√2, 48, 61, 63, 48√2, 87, 111, 87√2, 135, 111√2.

Code: 1355 0 87 1114 111 111 1113 222 111 244 135 87 203 159 91 102 169 101 631 222 111 103 169 91 52 174 96 353 174 61 482 222 48 43 139 87 307 139 91 877 0 87 870 87 87 264 113 61 263 139 61 611 174 61 483 222 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)