A219774 - OEIS

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A219774

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

4, 6, 14, 33, 65, 114, 189, 298, 450, 655, 924, 1269, 1703, 2240, 2895, 3684, 4624, 5733, 7030, 8535, 10269, 12254, 14513, 17070, 19950, 23179, 26784, 30793, 35235, 40140, 45539, 51464, 57948, 65025, 72730, 81099, 90169, 99978, 110565, 121970, 134234

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OFFSET

1,1

COMMENTS

Row 3 of A219773.

LINKS

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

FORMULA

Empirical: a(n) = (1/24)*n^4 + (1/4)*n^3 - (13/24)*n^2 + (17/4)*n for n>4.

Conjectures from Colin Barker, Jul 27 2018: (Start)

G.f.: x*(4 - 14*x + 24*x^2 - 17*x^3 + 5*x^5 + 3*x^6 - 6*x^7 + 2*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>9.

(End)

EXAMPLE

Some solutions for n=3:

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

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

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

CROSSREFS

Cf. A219773.

Sequence in context: A319766 A373567 A108516 * A274208 A077068 A277059

Adjacent sequences: A219771 A219772 A219773 * A219775 A219776 A219777

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 27 2012

STATUS

approved