A219520 Number of 3 X n arrays of the minimum value of corresponding elements and their horizontal, diagonal or antidiagonal neighbors in a random, but sorted with lexicographically nondecreasing rows and columns, 0..1 3 X n array.

4, 6, 11, 24, 43, 70, 111, 172, 260, 383, 550, 771, 1057, 1420, 1873, 2430, 3106, 3917, 4880, 6013, 7335, 8866, 10627, 12640, 14928, 17515, 20426, 23687, 27325, 31368, 35845, 40786, 46222, 52185, 58708, 65825, 73571, 81982, 91095, 100948, 111580

Offset

1,1

Comments

Row 3 of A219519.

Links

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

Formula

Empirical: a(n) = (1/24)*n^4 - (1/12)*n^3 - (13/24)*n^2 + (151/12)*n - 22 for n>4.

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

G.f.: x*(4 - 14*x + 21*x^2 - 11*x^3 - 7*x^4 + 11*x^5 - 4*x^7 + x^8) / (1 - x)^5.

a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n>6.

(End)

Example

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

Crossrefs

Cf. A219519.

Sequence in context: A336142 A091280 A363581 * A336343 A330459 A285994

Adjacent sequences: A219517 A219518 A219519 * A219521 A219522 A219523

Keyword

nonn

Author

R. H. Hardin, Nov 21 2012

Status

approved