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 A135443 Number of maximal directed trails in the labeled n-ladder graph P_2 X P_n. 0
 2, 8, 12, 40, 84, 144, 220, 312, 420, 544, 684, 840, 1012, 1200, 1404, 1624, 1860, 2112, 2380, 2664, 2964, 3280, 3612, 3960, 4324, 4704, 5100, 5512, 5940, 6384, 6844, 7320, 7812, 8320, 8844, 9384, 9940, 10512, 11100, 11704, 12324, 12960, 13612, 14280 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Table of n, a(n) for n=1..44. FORMULA For n > 2, a(n) = 4 * (n-2) * (2*n - 3) = A033586(n-2). - Max Alekseyev, May 04 2023 EXAMPLE For n = 4 the graph is .__.__.__. |__|__|__| Names of nodes: 1 2 3 4 a b c d Maximal directed paths which start from node 3: 34dcba123c 34dc32ba12 34dc321ab2 34dc321abc 3cd432ba12 3cd4321ab2 3cd4321abc 3cba1234dc 321abc34dc 321abcd43c There are also paths from nodes c,b,2. So n(4) = 4*10 = 40. CROSSREFS Apart from initial terms sequence is the same as A033586. Cf. A003682, A089243. Sequence in context: A285551 A143231 A104039 * A280092 A083546 A013190 Adjacent sequences: A135440 A135441 A135442 * A135444 A135445 A135446 KEYWORD nonn,walk AUTHOR Yasutoshi Kohmoto, Feb 18 2008 EXTENSIONS Edited and extended by Max Alekseyev, May 04 2023 STATUS approved

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Last modified May 18 18:37 EDT 2024. Contains 372664 sequences. (Running on oeis4.)