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A159191
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Number of n-colorings of the Robertson graph.
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1
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0, 0, 0, 24, 3490848, 3501104400, 564523119840, 31643453033640, 886834653776064, 15220684846368288, 181298924180884800, 1627952400490177080, 11672280987833510880, 69664869701930893104
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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COMMENTS
| The Robertson graph is the unique (4,5) cage: the quartic graph on 19 vertices (so 38 edges) with girth 5.
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LINKS
| Weisstein, Eric W. "Robertson Graph".
Weisstein, Eric W. "Chromatic Polynomial".
Timme, Marc; van Bussel, Frank; Fliegner, Denny; Stolzenberg, Sebastian (2009) "Counting complex disordered states by efficient pattern matching: chromatic polynomials and Potts partition functions", New J. Phys. 11 023001, doi: 10.1088/1367-2630/11/2/023001.
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FORMULA
| a(n) = n^19 -38*n^18 + ... (see Maple program).
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MAPLE
| a:= n-> n^19 -38*n^18 +703*n^17 -8436*n^16 +73761*n^15 -500004*n^14 +2727105*n^13 -12246808*n^12 +45913333*n^11 -144701057*n^10 +383839223*n^9 -853388854*n^8 +1574465385*n^7 -2370057775*n^6 +2835163369*n^5 -2587310804*n^4 +1685281636*n^3 -693467820*n^2 +134217080*n: seq (a(n), n=0..20);
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CROSSREFS
| The adjacency lists of the Robertson graph are included in A184945.
Cf. A115400, A140986, A157959, A157991, A157992, A157993, A158343, A158344, A158346, A158347, A158348, A158760, A158792, A158904, A159042, A159055, A159056, A159192, A159299, A166964, A173705, A173710.
Sequence in context: A013774 A088020 A172734 * A013820 A172803 A141643
Adjacent sequences: A159188 A159189 A159190 * A159192 A159193 A159194
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KEYWORD
| nonn
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AUTHOR
| Alois P. Heinz (heinz(AT)hs-heilbronn.de), Apr 05 2009
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