Primitive Perfect Isosceles Right Triangled Square
Title: _ 20:312AO GHM
Order: 20
Horizontal side: 312 Vertical side: 312
Elements: 8, 8√2, 12, 16, 12√2, 20, 15√2, 28, 30, 28√2, 56, 42√2, 72, 84, 114, 99√2, 156, 114√2, 198, 156√2.
Code: 1985 0 114 1564 156 156 1563 312 156 424 198 114 126 228 144 165 240 140 721 312 156 303 228 114 125 228 132 85 240 132 84 248 132 286 228 112 565 256 84 207 228 132 1145 0 0 1144 114 0 156 213 99 285 228 84 990 213 99 841 312 84
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)