Primitive Perfect Isosceles Right Triangled Square
Title: _ 20:328AP GHM
Order: 20
Horizontal side: 328 Vertical side: 328
Elements: 19√2, 20√2, 38, 40, 56, 40√2, 66, 47√2, 56√2, 80, 84, 94, 112, 80√2, 84√2, 94√2, 140, 112√2, 122√2, 188.
Code: 1887 0 328 560 188 328 561 244 328 842 328 244 841 328 328 1120 132 272 1121 244 272 1226 206 122 206 0 140 407 20 160 406 20 120 807 60 160 806 60 80 667 140 160 196 187 141 387 206 160 470 187 141 1405 0 0 947 140 94 940 234 94
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)