Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:127AD GHM

Order: 20

Horizontal side: 127 Vertical side: 127

Elements: 11√2, 16, 19, 22, 16√2, 19√2, 20√2, 32, 35, 38, 28√2, 40, 44, 32√2, 48, 35√2, 51, 40√2, 57, 46√2.

Code: 575 0 70 464 46 81 350 92 127 351 127 127 116 46 81 227 57 92 200 79 92 481 127 92 400 59 72 401 99 72 282 127 44 197 0 70 196 0 51 387 19 70 515 0 0 443 127 0 324 51 0 323 83 0 162 99 16 161 99 32

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)