Primitive Perfect Isosceles Right Triangled Square
Title: _ 20:312AB2of2 GHM
Order: 20
Horizontal side: 312 Vertical side: 312
Elements: 8√2, 16, 16√2, 24, 28, 24√2, 25√2, 28√2, 48, 50, 39√2, 50√2, 78, 56√2, 78√2, 128, 156, 117√2, 131√2, 156√2.
Code: 1565 0 156 1564 156 156 1316 181 181 250 181 181 782 78 78 781 78 156 392 117 117 1281 206 156 562 262 100 1170 117 117 483 262 52 502 312 50 80 214 52 244 238 28 243 262 28 503 312 0 167 206 44 160 222 44 284 234 0 283 262 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)