A219498 - OEIS

A219498

Number of n X 4 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..1 n X 4 array.

4, 7, 18, 35, 58, 88, 126, 173, 230, 298, 378, 471, 578, 700, 838, 993, 1166, 1358, 1570, 1803, 2058, 2336, 2638, 2965, 3318, 3698, 4106, 4543, 5010, 5508, 6038, 6601, 7198, 7830, 8498, 9203, 9946, 10728, 11550, 12413, 13318, 14266, 15258, 16295, 17378

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OFFSET

1,1

COMMENTS

Column 4 of A219502.

LINKS

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

FORMULA

Empirical: a(n) = (1/6)*n^3 + 1*n^2 + (23/6)*n - 7 for n>2.

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

G.f.: x*(4 - 9*x + 14*x^2 - 11*x^3 + 2*x^4 + x^5) / (1 - x)^4.

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

(End)

EXAMPLE

Some solutions for n=3:

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

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

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

CROSSREFS

Cf. A219502.

Sequence in context: A256216 A285462 A146387 * A358078 A219754 A289975

Adjacent sequences: A219495 A219496 A219497 * A219499 A219500 A219501

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 20 2012

STATUS

approved