Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:190AF GHM

Order: 20

Horizontal side: 190 Vertical side: 190

Elements: 12, 28, 20√2, 25√2, 28√2, 40, 50, 37√2, 54, 56, 40√2, 62, 68, 50√2, 72, 74, 54√2, 78, 56√2, 68√2.

Code: 787 0 190 500 78 190 501 128 190 252 153 165 621 190 190 370 153 165 280 28 140 281 56 140 727 56 140 200 116 128 741 190 128 562 56 56 561 56 112 400 96 108 401 136 108 542 190 54 127 56 68 680 68 68 681 136 68 543 190 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)