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A234875 Number of (n+1) X (1+1) 0..4 arrays with every 2 X 2 subblock having its diagonal sum differing from its antidiagonal sum by 1, with no adjacent elements equal (constant-stress tilted 1 X 1 tilings). 1
32, 68, 128, 268, 512, 1068, 2048, 4268, 8192, 17068, 32768, 68268, 131072, 273068, 524288, 1092268, 2097152, 4369068, 8388608, 17476268, 33554432, 69905068, 134217728, 279620268, 536870912, 1118481068, 2147483648, 4473924268 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

FORMULA

Empirical: a(n) = 5*a(n-2) - 4*a(n-4).

Conjectures from Colin Barker, Oct 16 2018: (Start)

G.f.: 4*x*(8 + 17*x - 8*x^2 - 18*x^3) / ((1 - x)*(1 + x)*(1 - 2*x)*(1 + 2*x)).

a(n) = (4 + (-2)^n + 49*2^n) / 3 for n even.

a(n) = ((-2)^n + 49*2^n) / 3 for n odd.

(End)

EXAMPLE

Some solutions for n=4:

3 2 3 2 0 1 1 3 4 3 2 3 4 2 1 0 1 3 0 2

2 0 2 0 2 4 0 1 2 0 0 2 1 0 4 2 0 1 2 3

4 1 4 3 1 2 2 4 4 3 2 3 4 2 1 0 2 4 0 2

2 0 3 1 2 4 0 1 2 0 0 2 1 0 3 1 1 2 3 4

4 3 4 3 0 3 1 3 4 1 3 4 4 2 1 0 2 4 0 2

CROSSREFS

Column 1 of A234882.

Sequence in context: A043935 A044134 A044515 * A153981 A264589 A100017

Adjacent sequences: A234872 A234873 A234874 * A234876 A234877 A234878

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 01 2014

STATUS

approved

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Last modified December 7 23:32 EST 2022. Contains 358671 sequences. (Running on oeis4.)