Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:254AE GHM

Order: 20

Horizontal side: 254 Vertical side: 254

Elements: 13√2, 28, 28√2, 48, 49, 36√2, 52, 56, 42√2, 52√2, 75, 76, 78, 84, 98, 104, 75√2, 78√2, 88√2, 101√2.

Code: 1012 101 153 884 88 166 756 101 179 787 176 254 786 176 176 136 88 166 755 101 104 362 212 140 493 101 104 843 212 56 422 254 98 526 0 52 1045 52 0 761 128 104 487 128 104 983 254 0 287 128 56 286 128 28 567 156 56 525 0 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)