Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:100BE GHM

Order: 20

Horizontal side: 100 Vertical side: 100

Elements: 1, 4, 3√2, 5, 4√2, 6, 7, 5√2, 7√2, 9√2, 14, 18, 25, 32, 36, 32√2, 34√2, 36√2, 64, 50√2.

Code: 645 0 36 504 50 50 346 66 66 90 66 66 70 57 57 181 75 57 255 75 32 141 64 50 52 69 45 53 69 40 65 69 39 47 64 40 40 68 40 11 69 40 34 72 36 73 75 32 365 0 0 364 36 0 320 68 32 321 100 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)