OFFSET
3,1
COMMENTS
The Hausdorff metric defines a distance between sets. Using this distance we can define line segments with sets as endpoints. Create two sets from the vertices of the parts A and B (with |A| = 5) of a complete bipartite graph K(5,n) (with n at least 3) missing two edges, where the removed edges are incident to the same point in A. Points in the sets A and B that correspond to vertices that are connected by edges are the same Euclidean distance apart. 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 (with n at least 3) matrices with two fixed zero entries in the same row 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 incident to the same vertex in A.
LINKS
Steven Schlicker, Roman Vasquez, and Rachel Wofford, Integer Sequences from Configurations in the Hausdorff Metric Geometry via Edge Covers of Bipartite Graphs, J. Int. Seq. (2023) Vol. 26, Art. 23.6.6.
Index entries for linear recurrences with constant coefficients, signature (57,-1002,6562,-15381,9765).
FORMULA
a(n) = 225*31^(n-2) - 421*15^(n-2) + 250*7^(n-2) - 58*3^(n-2) + 4.
From Colin Barker, Oct 13 2020: (Start)
G.f.: 16*x^3*(140 + 347*x + 1034*x^2 - 261*x^3) / ((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) for n>7.
(End)
MAPLE
a:= proc(n) 225*31^(n-2) - 421*15^(n-2)+250*7^(n-2)-58*3^(n-2)+4 end proc: seq(a(n), n=3..20);
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.
KEYWORD
easy,nonn
AUTHOR
Steven Schlicker, Aug 26 2020
STATUS
approved