Primitive Perfect Isosceles Right Triangled Square

Title: d 20:241AA GHM

Order: 20

Horizontal side: 241 Vertical side: 241

Elements: 8, 8√2, 23√2, 34, 40, 45, 46, 40√2, 45√2, 46√2, 69, 74, 80, 82, 90, 69√2, 98, 103, 127, 98√2.

Code: 1037 0 241 803 103 161 402 143 201 401 143 241 987 143 241 986 143 143 743 143 127 236 0 138 467 23 161 466 23 115 347 69 161 82 151 135 692 69 69 83 151 127 905 151 45 1275 69 0 821 151 127 693 69 0 454 196 0 453 241 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)