Primitive Perfect Isosceles Right Triangled Square

Title: _ 20:190AN GHM

Order: 20

Horizontal side: 190 Vertical side: 190

Elements: 4√2, 8, 8√2, 14, 12√2, 14√2, 16√2, 28, 27√2, 28√2, 40, 42, 54, 66, 68, 54√2, 82, 68√2, 108, 95√2.

Code: 1085 0 82 954 95 95 686 122 122 276 95 95 685 122 54 825 0 0 661 66 82 427 66 82 140 108 82 280 94 68 281 122 68 147 122 54 540 136 54 541 190 54 122 78 28 84 74 32 83 82 32 407 82 40 44 78 28 166 66 16

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)