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A183276 Half the number of n X n X n triangular binary arrays with each element having no more than two neighbors unequal to itself. 1
1, 4, 11, 26, 60, 132, 290, 620, 1322, 2777, 5848, 12169, 25419, 52590, 109375, 225532, 467758, 962536, 1993088, 4096214, 8473290, 17401047, 35973146, 73841057, 152593325, 313133216, 646942003, 1327337686, 2741920392, 5625006348 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..37

FORMULA

Empirical: a(n) = a(n-1) + 4*a(n-2) - 3*a(n-3) + 3*a(n-4) - 6*a(n-5) - 9*a(n-6) + 3*a(n-7) + 2*a(n-8) + a(n-9) + a(n-10).

Empirical g.f.: x*(1 + 3*x + 3*x^2 + 2*x^3 - x^4 - 5*x^5 - 4*x^6 + 3*x^7 - x^8 + x^9) / ((1 - x - x^2)*(1 + x^2 - x^4)*(1 - 4*x^2 - x^4)). - Colin Barker, Mar 27 2018

EXAMPLE

Some solutions for 5 X 5 X 5 with a(1,1)=0:

......0..........0..........0..........0..........0..........0..........0

.....1.1........0.0........0.1........1.1........0.0........1.1........0.0

....1.1.1......0.0.0......0.1.1......1.1.1......0.0.1......1.1.1......0.0.0

...0.0.0.0....1.1.1.1....0.1.1.0....0.0.0.0....0.0.1.1....1.1.1.1....1.1.1.1

..0.0.0.0.0..0.1.1.1.0..0.1.1.0.0..1.0.0.0.1..0.0.1.1.1..0.0.0.0.0..1.1.1.1.0

CROSSREFS

Sequence in context: A125128 A034334 A036891 * A268775 A294840 A014630

Adjacent sequences:  A183273 A183274 A183275 * A183277 A183278 A183279

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 03 2011

STATUS

approved

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Last modified April 1 05:04 EDT 2020. Contains 333155 sequences. (Running on oeis4.)