Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:114AW2of2 GHM

Order: 20

Horizontal side: 114 Vertical side: 114

Elements: 4√2, 6, 8, 6√2, 8√2, 12, 10√2, 15, 14√2, 21, 18√2, 28, 21√2, 36, 28√2, 42, 36√2, 39√2, 72, 57√2.

Code: 725 0 42 574 57 57 396 75 75 180 75 75 151 72 57 217 72 57 210 93 57 425 0 0 284 28 14 283 56 14 85 56 34 84 64 34 123 72 30 67 72 36 360 78 36 361 114 36 102 66 24 44 60 30 64 66 24 144 42 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)