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A203454 Number of n X 2 0..2 arrays with every nonzero element less than or equal to at least two horizontal and vertical neighbors. 1
1, 3, 9, 22, 63, 209, 686, 2228, 7365, 24619, 82433, 276500, 929936, 3133114, 10566260, 35661359, 120433051, 406897030, 1375168827, 4648638160, 15716950105, 53145110566, 179719928744, 607794550141, 2055594816788, 6952369432018 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 2 of A203460.

LINKS

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

FORMULA

Empirical: a(n) = 6*a(n-1) -12*a(n-2) +19*a(n-3) -32*a(n-4) +15*a(n-5) -13*a(n-6) +13*a(n-7) +10*a(n-8) +7*a(n-9) +5*a(n-10) +a(n-11).

Empirical g.f.: x*(1 - 3*x + 3*x^2 - 15*x^3 + 14*x^4 + 5*x^5 + 26*x^6 + 18*x^7 + 12*x^8 + 6*x^9 + x^10) / (1 - 6*x + 12*x^2 - 19*x^3 + 32*x^4 - 15*x^5 + 13*x^6 - 13*x^7 - 10*x^8 - 7*x^9 - 5*x^10 - x^11). - Colin Barker, Jun 04 2018

EXAMPLE

Some solutions for n=5:

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

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

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

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

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

CROSSREFS

Cf. A203460.

Sequence in context: A032284 A329163 A296582 * A197666 A146009 A326007

Adjacent sequences:  A203451 A203452 A203453 * A203455 A203456 A203457

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 02 2012

STATUS

approved

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Last modified September 28 10:48 EDT 2021. Contains 347714 sequences. (Running on oeis4.)