Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:234AA GHM

Order: 20

Horizontal side: 234 Vertical side: 234

Elements: 11√2, 20, 22, 22√2, 38, 37√2, 38√2, 64, 66, 74, 76, 54√2, 57√2, 84, 86, 66√2, 94, 74√2, 75√2, 84√2.

Code: 865 0 148 754 75 159 643 150 170 847 150 234 846 150 150 116 75 159 225 86 148 224 108 148 763 130 94 382 168 132 201 150 170 742 74 74 544 54 94 383 168 94 662 234 66 574 111 37 943 168 0 743 74 0 372 111 37 663 234 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)