Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:176AV GHM

Order: 20

Horizontal side: 176 Vertical side: 176

Elements: 5, 5√2, 10, 15, 14√2, 20, 25, 28, 23√2, 25√2, 42, 45, 46, 56, 46√2, 51√2, 74, 60√2, 102, 88√2.

Code: 1025 0 74 884 88 88 606 116 116 283 116 88 455 116 71 144 102 74 423 116 46 745 0 0 514 51 23 257 116 71 250 141 71 201 161 71 155 161 56 57 161 56 56 161 51 107 166 56 563 176 0 236 51 23 465 74 0 464 120 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)