Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:254AH GHM

Order: 20

Horizontal side: 254 Vertical side: 254

Elements: 13√2, 28, 28√2, 48, 36√2, 52, 56, 42√2, 52√2, 75, 76, 78, 84, 62√2, 98, 101, 104, 75√2, 78√2, 101√2.

Code: 1015 0 153 1014 101 153 520 202 254 521 254 254 626 88 140 765 150 126 1041 254 202 757 0 153 750 75 153 134 88 140 487 150 126 843 198 42 287 198 126 280 226 126 567 198 98 983 254 0 787 0 78 780 78 78 364 114 42 424 156 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)