Primitive Perfect Isosceles Right Triangled Square
Title: _ 20:217AO GHM
Order: 20
Horizontal side: 217 Vertical side: 217
Elements: 7, 7√2, 14, 20, 21, 20√2, 21√2, 30, 25√2, 40, 30√2, 35√2, 50, 40√2, 70, 50√2, 75√2, 117, 122, 167.
Code: 1677 0 217 256 142 192 507 167 217 506 167 167 1223 142 70 752 217 117 1173 217 0 206 0 50 405 20 30 404 60 30 703 100 0 352 135 35 214 121 49 213 142 49 205 0 30 141 135 49 72 142 42 71 142 49 305 0 0 304 30 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)