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A184030
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1/16 the number of (n+1) X (n+1) 0..3 arrays with all 2 X 2 subblocks having the same four values.
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2
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16, 40, 82, 166, 322, 634, 1234, 2434, 4786, 9490, 18802, 37426, 74482, 148594, 296434, 592114, 1182706, 2363890, 4724722, 9446386, 18886642, 37767154, 75522034, 151031794, 302039026, 604053490, 1208057842, 2416066546, 4832034802, 9663971314, 19327746034, 38655295474
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OFFSET
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1,1
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LINKS
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FORMULA
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a(n) = 3*a(n-1) - 6*a(n-3) + 4*a(n-4).
G.f.: 2*x*(8 - 4*x - 19*x^2 + 8*x^3)/((1 - x)*(1 - 2*x)*(1 - 2*x^2)). (End)
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EXAMPLE
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Some solutions for 4X4
..1..3..1..1....3..0..3..0....2..2..2..2....0..0..0..0....1..0..0..0
..1..1..1..3....0..1..0..1....1..3..1..3....2..2..2..2....0..2..1..2
..1..3..1..1....0..3..0..3....2..2..2..2....0..0..0..0....1..0..0..0
..1..1..1..3....1..0..1..0....3..1..3..1....2..2..2..2....0..2..1..2
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PROG
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(PARI) Vec(2*(8 - 4*x - 19*x^2 + 8*x^3)/((1 - x)*(1 - 2*x)*(1 - 2*x^2)) + O(x^30)) \\ Andrew Howroyd, Mar 09 2024
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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