A219579 Number of 2 X n arrays of the minimum value of corresponding elements and their horizontal or vertical neighbors in a random, but sorted with lexicographically nondecreasing rows and nonincreasing columns, 0..3 2 X n array.

4, 13, 51, 132, 277, 514, 881, 1429, 2225, 3355, 4927, 7074, 9957, 13768, 18733, 25115, 33217, 43385, 56011, 71536, 90453, 113310, 140713, 173329, 211889, 257191, 310103, 371566, 442597, 524292, 617829, 724471, 845569, 982565, 1136995, 1310492

Offset

1,1

Comments

Row 2 of A219578.

Links

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

Formula

Empirical: a(n) = (1/40)*n^5 - (5/24)*n^4 + (79/24)*n^3 - (91/24)*n^2 + (161/60)*n - 1 for n>1.

Conjectures from Colin Barker, Jul 26 2018: (Start)

G.f.: x*(4 - 11*x + 33*x^2 - 59*x^3 + 50*x^4 - 17*x^5 + 3*x^6) / (1 - x)^6.

a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6) for n>7.

(End)

Example

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

Crossrefs

Cf. A219578.

Sequence in context: A002746 A149459 A149460 * A300122 A149461 A056276

Adjacent sequences: A219576 A219577 A219578 * A219580 A219581 A219582

Keyword

nonn

Author

R. H. Hardin, Nov 23 2012

Status

approved