Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:186BK GHM

Order: 20

Horizontal side: 186 Vertical side: 186

Elements: 2, 2√2, 4, 4√2, 8, 10, 8√2, 10√2, 16, 20, 16√2, 21√2, 42, 42√2, 62, 82, 62√2, 72√2, 124, 93√2.

Code: 1245 0 62 934 93 93 726 114 114 216 93 93 162 130 98 163 130 82 82 138 90 83 138 82 42 142 86 43 142 82 22 144 84 23 144 82 422 186 42 107 114 82 106 114 72 207 124 82 823 144 0 625 0 0 624 62 0 423 186 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)