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A235271 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 5 (constant-stress 1 X 1 tilings). 1
40, 100, 208, 520, 1120, 2800, 6208, 15520, 35200, 88000, 203008, 507520, 1185280, 2963200, 6980608, 17451520, 41359360, 103398400, 246059008, 615147520, 1467965440, 3669913600, 8774238208, 21935595520, 52511211520, 131278028800 (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) = 10*a(n-2) - 24*a(n-4).

Conjectures from Colin Barker, Oct 17 2018: (Start)

G.f.: 4*x*(2 + 5*x)*(5 - 24*x^2) / ((1 - 2*x)*(1 + 2*x)*(1 - 6*x^2)).

a(n) = (-2)^n + 9*2^n + 6^((1/2)*(-1+n))*(12-12*(-1)^n + 5*sqrt(6) + 5*(-1)^n*sqrt(6)).

(End)

EXAMPLE

Some solutions for n=4:

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

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

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

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

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

CROSSREFS

Column 1 of A235280.

Sequence in context: A185791 A092889 A235280 * A033832 A235017 A043219

Adjacent sequences:  A235268 A235269 A235270 * A235272 A235273 A235274

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 05 2014

STATUS

approved

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Last modified September 28 20:34 EDT 2022. Contains 357081 sequences. (Running on oeis4.)