Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:127AF GHM

Order: 20

Horizontal side: 127 Vertical side: 127

Elements: 2√2, 6√2, 12, 12√2, 21, 16√2, 25, 18√2, 21√2, 32, 25√2, 36, 26√2, 38, 42, 52, 38√2, 64, 51√2, 53√2.

Code: 647 0 127 380 64 127 381 102 127 252 127 102 251 127 127 516 76 51 266 0 63 527 26 89 363 78 53 182 96 71 124 90 77 123 102 77 64 96 71 425 0 21 166 26 37 327 42 53 530 74 53 24 76 51 215 0 0 214 21 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)