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A230942
Number of (n+3) X (1+3) 0..3 white square subarrays x(i,j) with each element diagonally or antidiagonally next to at least one element with value (x(i,j)+1) mod 4, and upper left element zero.
2
6, 16, 76, 314, 1170, 4584, 18208, 71242, 278758, 1094600, 4294812, 16840082, 66052162, 259099696, 1016260448, 3986056882, 15634778470, 61325029216, 240537044748, 943467829258, 3700602618386, 14515016732376, 56932811822272
OFFSET
1,1
COMMENTS
Column 1 of A230949.
LINKS
FORMULA
Empirical: a(n) = 3*a(n-1) + 14*a(n-3) + a(n-4) - a(n-5).
Empirical g.f.: 2*x*(3 - x + 14*x^2 + x^3 - x^4) / (1 - 3*x - 14*x^3 - x^4 + x^5). - Colin Barker, Mar 18 2018
EXAMPLE
Some solutions for n=2:
..0..x..0..x....0..x..2..x....0..x..0..x....0..x..0..x....0..x..0..x
..x..1..x..3....x..1..x..3....x..1..x..1....x..1..x..1....x..1..x..3
..2..x..2..x....0..x..0..x....0..x..2..x....2..x..2..x....0..x..2..x
..x..3..x..1....x..3..x..3....x..3..x..1....x..3..x..1....x..1..x..1
..2..x..0..x....2..x..2..x....2..x..0..x....2..x..0..x....0..x..0..x
CROSSREFS
Cf. A230949.
Sequence in context: A083885 A350649 A211954 * A188570 A009352 A056204
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 01 2013
STATUS
approved