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A221442 Hilltop maps: number of n X 4 binary arrays indicating the locations of corresponding elements not exceeded by any horizontal or antidiagonal neighbor in a random 0..1 n X 4 array. 1
9, 117, 1465, 18393, 230845, 2897357, 36364977, 456419681, 5728560373, 71899621813, 902417942313, 11326320232169, 142157556964077, 1784230940565533, 22394026158604769, 281069224947245681 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 4 of A221446.

LINKS

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

FORMULA

Empirical: a(n) = 9*a(n-1) + 42*a(n-2) + 34*a(n-3) - 21*a(n-4) - 11*a(n-5) - 4*a(n-6).

Empirical g.f.: x*(9 + 36*x + 34*x^2 - 12*x^3 - 11*x^4 - 8*x^5) / (1 - 9*x - 42*x^2 - 34*x^3 + 21*x^4 + 11*x^5 + 4*x^6). - Colin Barker, Aug 05 2018

EXAMPLE

Some solutions for n=3:

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

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

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

CROSSREFS

Cf. A221446.

Sequence in context: A092913 A022607 A139740 * A196663 A292843 A180904

Adjacent sequences:  A221439 A221440 A221441 * A221443 A221444 A221445

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 17 2013

STATUS

approved

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Last modified May 28 18:24 EDT 2022. Contains 354122 sequences. (Running on oeis4.)