Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:178AK GHM

Order: 20

Horizontal side: 178 Vertical side: 178

Elements: 2√2, 7√2, 12√2, 24, 30, 24√2, 26√2, 38, 30√2, 44, 48, 52, 38√2, 60, 52√2, 74, 76, 59√2, 88, 74√2.

Code: 887 0 178 763 88 102 382 126 140 381 126 178 527 126 178 526 126 126 76 119 133 590 119 133 126 0 90 247 12 102 240 36 102 264 62 76 605 0 30 481 60 78 22 62 76 447 60 74 740 104 74 741 178 74 305 0 0 304 30 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)