Primitive Perfect Isosceles Right Triangled Square
Title: _ 20:160AA GHM
Order: 20
Horizontal side: 160 Vertical side: 160
Elements: 16, 20, 15√2, 16√2, 24, 20√2, 30, 32, 24√2, 25√2, 32√2, 50, 55, 56, 60, 64, 50√2, 55√2, 60√2, 85.
Code: 607 0 160 606 0 100 567 60 160 240 116 160 241 140 160 202 160 140 201 160 160 853 160 55 320 92 136 321 124 136 162 140 120 161 140 136 647 60 104 502 50 50 156 60 40 307 75 55 550 105 55 551 160 55 503 50 0 252 75 25
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)