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 A340174 Number of sets in the geometry determined by the Hausdorff metric at each location between two sets defined by a complete bipartite graph K(5,n) (with n at least 3) missing two edges, where the two removed edges are not incident to the same vertex in the 5-point set but are incident to the same vertex in the other set. 0
 2792, 140114, 5366288, 183405386, 5953824632, 188681559554, 5911452093728, 184194287464826, 5724142958302472, 177660449252559794, 5510655708296433968, 170878064308411409066, 5297936128237164553112, 164246762516365548788834, 5091810779768636860563008 (list; graph; refs; listen; history; text; internal format)
 OFFSET 3,1 COMMENTS Start with a complete bipartite graph K(5,n) with vertex sets A and B where |A| = 5 and |B| is at least 3. We can arrange the points in sets A and B such that h(A,B) = d(a,b) for all a in A and b in B, where h is the Hausdorff metric. The pair [A,B] is a configuration. Then a set C is between A and B at location s if h(A,C) = h(C,B) = h(A,B) and h(A,C) = s. Call a pair ab, where a is in A and b is in B an edge. This sequence provides the number of sets between sets A' and B' at location s in a new configuration [A',B'] obtained from [A,B] by removing two edges, where the two removed edges are not incident to the same point in A but are incident to the same point in B. So this sequence tells the number of sets at each location on the line segment between A' and B'. Number of {0,1} 5 X n matrices (with n at least 3) with two fixed zero entries in the same column and no zero rows or columns. Take a complete bipartite graph K(5,n) (with n at least 3) having parts A and B where |A| = 5. This sequence gives the number of edge covers of the graph obtained from this K(5,n) graph after removing two edges, where the two removed edges are not incident to the same vertex in A but are incident to the same vertex in B. REFERENCES S. Schlicker, R. Vasquez, R. Wofford, Integer Sequences from Configurations in the Hausdorff Metric Geometry via Edge Covers of Bipartite Graphs. In preparation. LINKS Index entries for linear recurrences with constant coefficients, signature (57,-1002,6562,-15381,9765). FORMULA a(n) = 7*31^(n-1) - 23*15^(n-1) + 4*7^n - 5*3^(n) + 3. From Alejandro J. Becerra Jr., Feb 12 2021: (Start) G.f.: 2*x^3*(126945*x^4 - 199953*x^3 + 88687*x^2 - 9515*x + 1396)/((1 - x)*(1 - 3*x)*(1 - 7*x)*(1 - 15*x)*(1 - 31*x)). a(n) = 57*a(n-1) - 1002*a(n-2) + 6562*a(n-3) - 15381*a(n-4) + 9765*a(n-5). (End) MATHEMATICA Array[7*31^(# - 1) - 23*15^(# - 1) + 4*7^# - 5*3^(#) + 3 &, 15, 3] (* Michael De Vlieger, Jan 12 2021 *) LinearRecurrence[{57, -1002, 6562, -15381, 9765}, {2792, 140114, 5366288, 183405386, 5953824632}, 20] (* Harvey P. Dale, Aug 11 2021 *) CROSSREFS Sequences of segments from removing edges from bipartite graphs A335608-A335613, A337416-A337418, A340173-A340175, A340199-A340201, A340897-A340899, A342580, A342796, A342850, A340403-A340405, A340433-A340438, A341551-A341553, A342327-A342328, A343372-A343374, A343800. Polygonal chain sequences A152927, A152928, A152929, A152930, A152931, A152932, A152933, A152934, A152939. Cf. A048291 (number of {0,1} n X n matrices with no zero rows or columns). Sequence in context: A106300 A252601 A233923 * A252900 A236637 A236943 Adjacent sequences:  A340171 A340172 A340173 * A340175 A340176 A340177 KEYWORD easy,nonn AUTHOR Steven Schlicker, Dec 30 2020 STATUS approved

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Last modified June 26 01:42 EDT 2022. Contains 354870 sequences. (Running on oeis4.)