Primitive Perfect Isosceles Right Triangled Square

Title: __ 19:156AE1of2 GHM

Order: 19

Horizontal side: 156 Vertical side: 156

Elements: 4, 4√2, 5√2, 10, 24, 20√2, 32, 24√2, 34, 36, 29√2, 44, 32√2, 34√2, 44√2, 68, 78, 88, 78√2.

Code: 885 0 68 784 78 78 783 156 78 101 88 78 52 93 73 344 122 44 343 156 44 290 93 73 685 0 0 324 32 36 323 64 36 247 64 68 42 68 40 244 88 20 440 112 44 441 156 44 43 68 36 202 88 20 361 68 36

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)