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 A340173 Number of sets in the geometry determined by the Hausdorff metric at each location between two sets defined by a complete bipartite graph K(4,n) (with n at least 3) missing two edges, where the two removed edges are not incident to the same vertex in the 4-point set but are incident to the same vertex in the other set. 36
 344, 7568, 133232, 2145368, 33235784, 506005088, 7642599392, 115007387048, 1727691783224, 25933450204208, 389128287094352, 5837810104155128, 87573352325069864, 1313643690750940928, 19704959203995442112, 295576514963872161608 (list; graph; refs; listen; history; text; internal format)
 OFFSET 3,1 COMMENTS Start with a complete bipartite graph K(4,n) with vertex sets A and B where |A| = 4 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} 4 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(4,n) (with n at least 3) having parts A and B where |A| = 4. This sequence gives the number of edge covers of the graph obtained from this K(4,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 (26,-196,486,-315). FORMULA a(n) = 3*15^(n-1) - 8*7^(n-1) + 7*3^(n-1) - 2. From Stefano Spezia, Dec 30 2020: (Start) G.f.: 8*x^3*(43 - 172*x + 486*x^2 - 315*x^3)/(1 - 26*x + 196*x^2 - 486*x^3 + 315*x^4). a(n) = 26*a(n-1) - 196*a(n-2) + 486*a(n-3) - 315*a(n-4) for n > 6. (End) 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. Number of {0,1} n X n matrices with no zero rows or columns A048291. Sequence in context: A250921 A262791 A186935 * A115221 A065499 A183673 Adjacent sequences:  A340170 A340171 A340172 * A340174 A340175 A340176 KEYWORD easy,nonn AUTHOR Steven Schlicker, Dec 30 2020 STATUS approved

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Last modified May 20 01:46 EDT 2022. Contains 353847 sequences. (Running on oeis4.)