Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:256AX GHM

Order: 20

Horizontal side: 256 Vertical side: 256

Elements: 10√2, 20, 20√2, 27√2, 40, 31√2, 44, 40√2, 62, 44√2, 70, 53√2, 80, 62√2, 88, 106, 114, 88√2, 93√2, 106√2.

Code: 1065 0 150 1064 106 150 440 212 256 441 256 256 880 168 212 881 256 212 805 0 70 534 53 97 276 53 97 1147 80 124 316 163 93 627 194 124 626 194 62 930 163 93 705 0 0 404 40 30 403 80 30 204 60 10 203 80 10 104 70 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)