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A051926
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Number of independent sets of nodes in graph C_4 x P_n (n>2).
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0
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1, 7, 35, 181, 933, 4811, 24807, 127913, 659561, 3400911, 17536203, 90422365, 466247117, 2404121747, 12396433487, 63920042065, 329592522065, 1699486218903, 8763103574515, 45185411569413, 232990675202677
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| Number of ways zero or more black and white stones can be placed on the points of a 2 X n grid such that no white stones are adjacent to any black stones. A078057 is a related case, where the grid is 1 X n. - Wayne VanWeerthuizen (waynemv(AT)yahoo.com), May 04 2004
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FORMULA
| a[0]=1, a[n]=5*a[n-1]+a[n-2]-a[n-3]. - Wayne VanWeerthuizen (waynemv(AT)yahoo.com), May 04 2004
a(n) = a(n-1) + 17*a(n-2) + 23*a(n-3) + a(n-4) - 9*a(n-5) - a(n-6) + a(n-7)
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CROSSREFS
| Sequence in context: A005055 A037506 A037689 * A026128 A026157 A025184
Adjacent sequences: A051923 A051924 A051925 * A051927 A051928 A051929
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KEYWORD
| easy,nonn
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AUTHOR
| Stephen G. Penrice (spenrice(AT)ets.org), Dec 19 1999
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EXTENSIONS
| More terms from James A. Sellers (sellersj(AT)math.psu.edu), Dec 20 1999
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