Primitive Perfect Isosceles Right Triangled Square
Title: _ 20:312AC GHM
Order: 20
Horizontal side: 312 Vertical side: 312
Elements: 2, 2√2, 5√2, 10, 10√2, 20, 20√2, 40, 40√2, 76, 78, 80, 76√2, 77√2, 78√2, 80√2, 154, 156, 158, 156√2.
Code: 1587 0 312 776 81 235 1547 158 312 1566 156 156 50 81 235 766 0 154 107 76 230 100 86 230 207 76 220 200 96 220 407 76 200 400 116 200 807 76 160 806 76 80 22 158 158 1565 156 0 765 0 78 25 76 78 787 0 78 780 78 78
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)