Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:256BF GHM

Order: 20

Horizontal side: 256 Vertical side: 256

Elements: 3, 3√2, 6, 9, 9√2, 10√2, 20, 15√2, 30, 40, 40√2, 68, 49√2, 80, 69√2, 98, 118, 138, 108√2, 128√2.

Code: 1385 0 118 1284 128 128 1086 148 148 203 148 128 685 148 80 104 138 118 303 148 98 1185 0 0 694 69 49 496 69 49 985 118 0 154 133 83 96 139 89 63 139 83 95 139 80 34 136 80 33 139 80 801 216 80 402 256 40 403 256 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)