Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:188AJ GHM

Order: 20

Horizontal side: 188 Vertical side: 188

Elements: 1√2, 2, 2√2, 3√2, 6, 6√2, 12, 40, 34√2, 52, 40√2, 62, 46√2, 68, 52√2, 74, 80, 68√2, 102, 74√2.

Code: 745 0 114 744 74 114 400 148 188 401 188 188 460 108 148 801 188 148 627 0 114 66 56 108 127 62 114 36 53 105 65 56 102 10 53 105 526 0 52 27 52 104 20 54 104 1027 52 102 340 154 102 680 120 68 681 188 68 525 0 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)