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A224354 Number of 3 X n 0..2 arrays with diagonals and antidiagonals unimodal and rows nondecreasing. 1
27, 216, 788, 2321, 5840, 13052, 26610, 50423, 90012, 152912, 249120, 391589, 596768, 885188, 1282094, 1818123, 2530028, 3461448, 4663724, 6196761, 8129936, 10543052, 13527338, 17186495, 21637788, 27013184, 33460536, 41144813, 50249376 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 3 of A224353.

LINKS

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

FORMULA

Empirical: a(n) = (23/360)*n^6 + (19/40)*n^5 + (235/72)*n^4 + (61/8)*n^3 + (1921/180)*n^2 + (189/10)*n + 3 for n>1.

Conjectures from Colin Barker, Aug 29 2018: (Start)

G.f.: x*(27 + 27*x - 157*x^2 + 396*x^3 - 474*x^4 + 326*x^5 - 116*x^6 + 17*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..1....1..1..2....2..2..2....0..2..2....0..1..1....1..1..1....0..1..2

..1..1..2....1..1..2....2..2..2....1..1..1....1..1..2....1..1..2....1..1..1

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

CROSSREFS

Cf. A224353.

Sequence in context: A224874 A125111 A016767 * A224013 A059827 A117688

Adjacent sequences:  A224351 A224352 A224353 * A224355 A224356 A224357

KEYWORD

nonn

AUTHOR

R. H. Hardin, Apr 04 2013

STATUS

approved

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Last modified September 29 22:05 EDT 2022. Contains 357092 sequences. (Running on oeis4.)