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A224134 Number of 3 X n 0..1 arrays with rows nondecreasing and antidiagonals unimodal. 1
8, 27, 58, 106, 175, 269, 392, 548, 741, 975, 1254, 1582, 1963, 2401, 2900, 3464, 4097, 4803, 5586, 6450, 7399, 8437, 9568, 10796, 12125, 13559, 15102, 16758, 18531, 20425, 22444, 24592, 26873, 29291, 31850, 34554, 37407, 40413, 43576, 46900, 50389, 54047 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 3 of A224133.

LINKS

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

FORMULA

Empirical: a(n) = (2/3)*n^3 + (5/2)*n^2 + (35/6)*n for n>1.

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

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

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

(End)

EXAMPLE

Some solutions for n=3:

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

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

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

CROSSREFS

Cf. A224133.

Sequence in context: A223950 A131620 A141227 * A213488 A151675 A211641

Adjacent sequences:  A224131 A224132 A224133 * A224135 A224136 A224137

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 31 2013

STATUS

approved

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Last modified November 18 19:59 EST 2019. Contains 329288 sequences. (Running on oeis4.)