Can this be done with Polya-Theoy? Given the graph of the dodecahedron. (20 vertices, 30 edges, 3-regular). - How many different orientations of the edges are possible for a given in-degree vector (i0, i1, i2, i3)? (Where i_k is the number of vertices with in-degree k.) --------------------------------------------------------------------------- The Dodecahedron Puzzle from the CFF: Torsten Sillke, 15.09.96 Contest 9 (reprinted in CFF 27, (1991) p5) Leo Links "inside the Icosahedron" Using the right number and the right combination of each of the four possible magnetic tetrahedral building blocks, we can construct a non-flipping model of the regular icosahedron. How many sets are possible and how many different arrangements exist for each set? w, x, y, z count the number of tetrahedra with 0, 1, 2, or 3 black dots. The digits 'a' to 'f' are standing for '10' to '15' (Hexadecimal Notation). The symmetry-group of the icosahedron has not been factored out. In this case its reflection-group S5 (order = 120) would be appropriate. A further symmetry is the white/black exchange: solutions(wxyz) = solutions(zyxw). It is better to analyze the problem by transforming to the dual polyhedron the dodecahedron where all edge are oriented. For all 2^30 orientations I counted the number of appearences of the different out-degree-seqences. wxyz solutions Computation Time 16 minutes on a HP 755 (99 MHz). ---------------- The sum of all solutions is 2^30 = 1073741824. 0aa0 3600000 0b81 11280000 0c62 9846720 0d43 2778240 0e24 215040 0f05 2048 18b0 11280000 1991 51906560 1a72 68856960 1b53 31683840 1c34 4707840 1d15 153600 26c0 9846720 27a1 68856960 2882 140757120 2963 104117120 2a44 27541440 2b25 2108160 2c06 20480 34d0 2778240 35b1 31683840 3692 104117120 3773 125736960 3854 57803520 3935 8995840 3a16 314880 42e0 215040 43c1 4707840 44a2 27541440 4583 57803520 4664 47280000 4745 14240640 4826 1247040 4907 13440 50f0 2048 51d1 153600 52b2 2108160 5393 8995840 5474 14240640 5555 8414208 5636 1621120 5717 65280 60c2 20480 61a3 314880 6284 1247040 6365 1621120 6446 670080 6527 67200 6608 320 7094 13440 7175 65280 7256 67200 7337 15360 8066 320 Who counts (generates) the symmetric solutions. As there are many symmetries many case have to be considered. If the numbers are known for each case the symmetry group can be factored out.