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A235541 Number of (n+1) X (1+1) 0..1 arrays with the sum of each 2 X 2 subblock two median terms lexicographically nondecreasing rowwise and columnwise. 2
16, 48, 141, 378, 988, 2482, 6109, 14712, 34896, 81612, 188725, 432046, 980620, 2208798, 4941909, 10990620, 24311440, 53516200, 117285181, 256007874, 556755036, 1206716778, 2607303661, 5617260448, 12069653488, 25869224292 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 1 of A235548.

LINKS

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

FORMULA

Empirical: a(n) = 4*a(n-1) - 14*a(n-3) + 5*a(n-4) + 18*a(n-5) - 4*a(n-6) - 8*a(n-7).

Empirical g.f.: x*(16 - 16*x - 51*x^2 + 38*x^3 + 68*x^4 - 24*x^5 - 32*x^6) / ((1 - x)*(1 + x)^3*(1 - 2*x)^3). - Colin Barker, Mar 19 2018

EXAMPLE

Some solutions for n=5:

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

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

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

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

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

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

CROSSREFS

Cf. A235548.

Sequence in context: A211590 A211584 A211598 * A109098 A223395 A202329

Adjacent sequences:  A235538 A235539 A235540 * A235542 A235543 A235544

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 12 2014

STATUS

approved

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Last modified October 18 14:08 EDT 2021. Contains 348068 sequences. (Running on oeis4.)