Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:91AA GHM

Order: 20

Horizontal side: 91 Vertical side: 91

Elements: 2√2, 4, 5, 11√2, 16, 17, 13√2, 15√2, 22, 16√2, 24, 26, 28, 32, 24√2, 26√2, 39, 43, 48, 52.

Code: 525 0 39 481 48 91 325 48 59 431 91 91 165 48 43 164 64 43 110 80 59 53 69 43 227 69 48 246 67 24 41 52 43 152 67 28 171 69 43 395 0 0 264 26 13 263 52 13 283 67 0 22 69 26 245 67 0 134 39 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)