Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:191AB1of2 GHM

Order: 20

Horizontal side: 191 Vertical side: 191

Elements: 2, 2√2, 3, 4, 3√2, 5, 4√2, 7, 22, 22√2, 44, 59, 44√2, 66, 81, 59√2, 88, 66√2, 110, 125.

Code: 1257 0 191 813 125 110 667 125 191 666 125 125 42 129 121 43 129 117 32 132 118 33 132 115 592 191 59 75 125 110 24 127 115 23 129 115 51 132 115 446 0 66 887 44 110 1103 132 0 445 0 22 593 191 0 225 0 0 224 22 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)