Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:366AL GHM

Order: 20

Horizontal side: 366 Vertical side: 366

Elements: 4, 4√2, 8, 6√2, 12, 12√2, 18, 18√2, 36, 27√2, 50, 54, 54√2, 104, 104√2, 154, 131√2, 208, 158√2, 262.

Code: 2627 0 366 2083 262 158 1042 366 262 1041 366 366 1316 235 131 546 0 104 1547 54 158 1580 208 158 274 235 131 545 0 50 505 0 0 361 36 50 182 54 32 181 54 50 126 42 20 66 36 14 125 42 8 81 50 8 42 54 4 41 54 8

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)