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A251081 Number of (n+1) X (1+1) 0..2 arrays with no 2 X 2 subblock having the sum of its diagonal elements greater than the absolute difference of its antidiagonal elements. 1
27, 83, 192, 420, 872, 1782, 3593, 7215, 14443, 28891, 57762, 115486, 230898, 461692, 923231, 1846265, 3692269, 7384217, 14768032, 29535584, 59070588, 118140498, 236280197, 472559475, 945117887, 1890234567, 3780467758, 7560933970 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

FORMULA

Empirical: a(n) = 5*a(n-1) - 8*a(n-2) + 2*a(n-3) + 7*a(n-4) - 7*a(n-5) + 2*a(n-6) for n>7.

Empirical g.f.: x*(27 - 52*x - 7*x^2 + 70*x^3 - 47*x^4 + 6*x^5 + 2*x^6) / ((1 - x)^4*(1 + x)*(1 - 2*x)). - Colin Barker, Nov 24 2018

EXAMPLE

Some solutions for n=4:

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

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

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

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

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

CROSSREFS

Column 1 of A251088.

Sequence in context: A042438 A251088 A044981 * A161340 A043182 A039359

Adjacent sequences:  A251078 A251079 A251080 * A251082 A251083 A251084

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 29 2014

STATUS

approved

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Last modified October 5 09:00 EDT 2022. Contains 357252 sequences. (Running on oeis4.)