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A224013 Number of 3 X n 0..2 arrays with rows nondecreasing and antidiagonals unimodal. 1
27, 216, 868, 2661, 6815, 15340, 31324, 59267, 105461, 178416, 289332, 452617, 686451, 1013396, 1461052, 2062759, 2858345, 3894920, 5227716, 6920973, 9048871, 11696508, 14960924, 18952171, 23794429, 29627168, 36606356, 44905713, 54718011 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 3 of A224012.

LINKS

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

FORMULA

Empirical: a(n) = (23/360)*n^6 + (27/40)*n^5 + (271/72)*n^4 + (65/8)*n^3 + (2101/180)*n^2 + (97/10)*n - 1 for n>1.

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

G.f.: x*(27 + 27*x - 77*x^2 + 176*x^3 - 199*x^4 + 129*x^5 - 43*x^6 + 6*x^7) / (1 - x)^7.

a(n) = 7*a(n-1) - 21*a(n-2) + 35*a(n-3) - 35*a(n-4) + 21*a(n-5) - 7*a(n-6) + a(n-7) for n>8.

(End)

EXAMPLE

Some solutions for n=3:

..0..0..0....1..1..1....0..0..1....0..1..2....0..1..2....1..2..2....1..1..2

..2..2..2....1..1..2....2..2..2....1..1..2....0..0..0....1..1..1....0..0..2

..1..2..2....1..2..2....1..1..2....1..1..2....0..0..2....1..1..1....0..1..1

CROSSREFS

Cf. A224012.

Sequence in context: A125111 A016767 A224354 * A059827 A117688 A272342

Adjacent sequences:  A224010 A224011 A224012 * A224014 A224015 A224016

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 30 2013

STATUS

approved

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Last modified January 29 16:58 EST 2020. Contains 331347 sequences. (Running on oeis4.)