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 A320099 Number of no-leaf subgraphs of the 5 X n grid. 2
 1, 50, 5193, 583199, 65485654, 7354266811, 825905301851, 92751581627976, 10416273692997679, 1169777980482365913, 131369486228240893660, 14753177269494392259423, 1656824927874469183283433, 186066281959642930757881316, 20895787297635543757965741097 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Also, the number of ways to lay unit-length matchsticks on a 5 X n grid of points in such a way that no end is "orphaned". LINKS Peter Kagey, Table of n, a(n) for n = 1..488 FORMULA Conjecture: a(n) = 103*a(n-1) + 1063*a(n-2) - 1873*a(n-3) - 20274*a(n-4) + 44071*a(n-5) - 10365*a(n-6) - 20208*a(n-7) + 5959*a(n-8) + 2300*a(n-9) - 500*a(n-10) for n > 10. EXAMPLE Three of the a(3) = 5193 subgraphs of the 5 X 3 grid with no leaf vertices are: +---+---+      +   +   +      +   +---+ |   |   |                         |   | +---+---+      +---+---+      +   +---+ |   |   |,     |   |   |, and          . +---+---+      +   +---+      +---+   + |   |   |      |   |          |   | +---+---+      +---+   +      +---+---+ |   |   |                         |   | +---+---+      +   +   +      +   +---+ CROSSREFS A093129 is analogous for 2 X (n+1) grids. A301976 is analogous for 3 X n grids. A320097 is analogous for 4 X n grids. Sequence in context: A174756 A231937 A230477 * A115436 A184555 A301992 Adjacent sequences:  A320096 A320097 A320098 * A320100 A320101 A320102 KEYWORD nonn AUTHOR Peter Kagey, Oct 05 2018 STATUS approved

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Last modified December 5 05:51 EST 2020. Contains 338944 sequences. (Running on oeis4.)