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A240778 Number of n X 3 0..1 arrays with no element equal to fewer vertical neighbors than horizontal neighbors, with new values 0..1 introduced in row major order. 1
1, 4, 20, 97, 459, 2187, 10442, 49861, 238068, 1136678, 5427201, 25912833, 123723975, 590735140, 2820536641, 13466994652, 64299801122, 307007207679, 1465843189533, 6998846289463, 33416841401200, 159552766705917 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

FORMULA

Empirical: a(n) = 5*a(n-1) - a(n-2) - a(n-3) + 4*a(n-4) - 4*a(n-5) - 3*a(n-6) + a(n-7).

Empirical g.f.: x*(1 + x)^2*(1 - 3*x + 6*x^2 - 7*x^3 + 2*x^4) / ((1 - x)*(1 - 4*x - 3*x^2 - 2*x^3 - 6*x^4 - 2*x^5 + x^6)). - Colin Barker, Oct 29 2018

EXAMPLE

Some solutions for n=4:

..0..1..0....0..1..0....0..1..0....0..1..0....0..1..0....0..1..0....0..1..0

..0..1..1....1..0..1....0..1..0....0..1..0....0..1..0....1..0..1....1..1..0

..0..1..1....0..1..1....1..0..1....1..1..0....0..0..1....1..1..0....1..0..0

..0..1..0....0..1..0....0..1..0....1..1..0....1..0..1....0..1..0....1..0..0

CROSSREFS

Column 3 of A240783.

Sequence in context: A057087 A151254 A232493 * A293710 A098225 A073532

Adjacent sequences:  A240775 A240776 A240777 * A240779 A240780 A240781

KEYWORD

nonn

AUTHOR

R. H. Hardin, Apr 12 2014

STATUS

approved

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Last modified September 20 12:13 EDT 2020. Contains 337264 sequences. (Running on oeis4.)