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A237629 Number of (n+1) X (n+1) 0..2 arrays with the upper median of every 2 X 2 subblock differing from its horizontal and vertical neighbors by exactly one. 1
81, 636, 1310, 2012, 4622, 9368, 18344, 44292, 102536, 211268, 402152, 1015572, 2337608, 4914788, 9150632, 23921652, 54827528, 116999108, 214315112, 574558932, 1312885448, 2831048228, 5126666792, 13988255412, 31897292168, 69273334148 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..36

FORMULA

Empirical: a(n) = 4*a(n-2) + 25*a(n-4) - 100*a(n-6) for n>11.

Empirical g.f.: x*(81 + 636*x + 986*x^2 - 532*x^3 - 2643*x^4 - 14580*x^5 - 24794*x^6 + 20120*x^7 + 44610*x^8 + 1100*x^9 - 4392*x^10) / ((1 - 2*x)*(1 + 2*x)*(1 - 5*x^2)*(1 + 5*x^2)). - Colin Barker, Oct 23 2018

EXAMPLE

Some solutions for n=5:

..1..0..0..1..2..1....1..0..2..1..0..1....2..1..0..1..2..2....1..0..1..2..0..1

..1..0..1..2..0..0....1..2..0..0..0..2....0..2..0..0..0..2....2..0..0..0..2..1

..0..0..2..1..0..1....2..1..0..1..2..1....0..1..2..1..0..1....1..2..1..0..1..2

..1..2..0..0..0..2....0..0..0..2..1..0....0..0..0..2..0..0....0..0..2..0..0..0

..2..1..0..1..2..0....0..1..2..0..0..0....2..1..0..1..2..1....1..0..1..2..1..0

..0..0..0..2..1..0....1..2..1..0..2..1....2..1..0..0..0..2....2..0..0..0..2..1

CROSSREFS

Diagonal of A237637.

Sequence in context: A322240 A185856 A185848 * A236720 A187441 A187433

Adjacent sequences:  A237626 A237627 A237628 * A237630 A237631 A237632

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 10 2014

STATUS

approved

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Last modified September 23 04:54 EDT 2020. Contains 337295 sequences. (Running on oeis4.)