Primitive Perfect Isosceles Right Triangled Square
Title: _ 20:50AH GHM
Order: 20
Horizontal side: 50 Vertical side: 50
Elements: 1, 1√2, 2, 3√2, 5, 6, 7, 5√2, 7√2, 10, 12, 16, 12√2, 18, 13√2, 19, 16√2, 18√2, 19√2, 32.
Code: 325 0 18 194 19 31 193 38 31 127 38 50 126 38 38 75 38 31 134 32 18 50 45 31 30 40 26 101 50 26 53 37 18 67 37 23 70 43 23 185 0 0 184 18 0 23 36 16 12 37 17 11 37 18 160 34 16 161 50 16
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)