A220154 Number of 2 X n arrays of the minimum value of corresponding elements and their horizontal or diagonal neighbors in a random, but sorted with lexicographically nondecreasing rows and nonincreasing columns, 0..2 2 X n array.

6, 11, 23, 50, 88, 137, 197, 268, 350, 443, 547, 662, 788, 925, 1073, 1232, 1402, 1583, 1775, 1978, 2192, 2417, 2653, 2900, 3158, 3427, 3707, 3998, 4300, 4613, 4937, 5272, 5618, 5975, 6343, 6722, 7112, 7513, 7925, 8348, 8782, 9227, 9683, 10150, 10628

Offset

1,1

Comments

Row 2 of A220153.

Links

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

Formula

Empirical: a(n) = (11/2)*n^2 - (23/2)*n + 8 for n>2.

Conjectures from Colin Barker, Mar 13 2018: (Start)

G.f.: x*(6 - 7*x + 8*x^2 + 8*x^3 - 4*x^4) / (1 - x)^3.

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>5.

(End)

Example

Some solutions for n=3
..0..0..0....0..0..0....2..0..0....1..0..1....0..0..0....1..1..1....1..0..0
..0..0..0....1..0..0....2..0..0....1..0..0....2..2..0....2..2..1....2..1..1

Crossrefs

Cf. A220153.

Sequence in context: A239767 A046616 A155449 * A362441 A309742 A362442

Adjacent sequences: A220151 A220152 A220153 * A220155 A220156 A220157

Keyword

nonn

Author

R. H. Hardin, Dec 06 2012

Status

approved