Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:166AG GHM

Order: 20

Horizontal side: 166 Vertical side: 166

Elements: 5, 5√2, 11, 9√2, 11√2, 18, 18√2, 32, 23√2, 27√2, 43, 32√2, 46, 54, 46√2, 69, 74, 60√2, 65√2, 74√2.

Code: 745 0 92 744 74 92 96 139 157 187 148 166 186 148 148 270 139 157 433 112 87 547 112 130 656 101 65 462 46 46 691 69 92 57 69 92 322 101 55 321 101 87 112 112 76 111 112 87 52 106 60 600 106 60 463 46 0 232 69 23

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)