Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:186AU GHM

Order: 20

Horizontal side: 186 Vertical side: 186

Elements: 15√2, 17√2, 20√2, 30, 34, 40, 46, 34√2, 52, 40√2, 41√2, 58, 60, 46√2, 52√2, 74, 54√2, 80, 82, 67√2.

Code: 825 0 104 674 67 119 520 134 186 521 186 186 156 67 119 307 82 134 540 112 134 741 186 134 585 0 46 414 41 63 176 41 63 345 58 46 344 92 46 803 126 0 402 166 40 401 166 80 202 186 60 603 186 0 465 0 0 464 46 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)