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A223919 Number of 2 X n 0..2 arrays with rows and antidiagonals unimodal and columns nondecreasing. 3
6, 36, 158, 548, 1600, 4102, 9503, 20299, 40570, 76704, 138348, 239630, 400700, 649642, 1024813, 1577669, 2376142, 3508636, 5088714, 7260552, 10205240, 14148014, 19366507, 26200111, 35060546, 46443736, 60943096, 79264338 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 2 of A223918.

LINKS

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

FORMULA

Empirical: a(n) = (1/10080)*n^8 + (1/504)*n^7 + (1/40)*n^6 + (109/720)*n^5 + (259/480)*n^4 + (173/144)*n^3 + (4877/2520)*n^2 + (481/420)*n + 1.

Conjectures from Colin Barker, Feb 23 2018: (Start)

G.f.: x*(6 - 18*x + 50*x^2 - 82*x^3 + 88*x^4 - 62*x^5 + 29*x^6 - 8*x^7 + x^8) / (1 - x)^9.

a(n) = 9*a(n-1) - 36*a(n-2) + 84*a(n-3) - 126*a(n-4) + 126*a(n-5) - 84*a(n-6) + 36*a(n-7) - 9*a(n-8) + a(n-9) for n>9.

(End)

EXAMPLE

Some solutions for n=3:

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

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

CROSSREFS

Cf. A223918.

Sequence in context: A224149 A055404 A223946 * A263952 A281394 A225380

Adjacent sequences:  A223916 A223917 A223918 * A223920 A223921 A223922

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 29 2013

STATUS

approved

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Last modified May 28 04:51 EDT 2020. Contains 334671 sequences. (Running on oeis4.)