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A184130
Number of n X 2 0..2 arrays with rows and columns in nondecreasing order.
1
6, 29, 112, 356, 972, 2359, 5217, 10704, 20647, 37818, 66287, 111865, 182651, 289698, 447814, 676515, 1001148, 1454203, 2076834, 2920610, 4049518, 5542241, 7494735, 10023130, 13266981, 17392896, 22598569, 29117247, 37222661, 47234452, 59524124
OFFSET
1,1
Column 2 of A184137.
FORMULA
Empirical: 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) (=polynomial of degree 8).
Conjectures from Colin Barker, Apr 12 2018: (Start)
G.f.: x*(2 - x)*(3 - 11*x + 28*x^2 - 42*x^3 + 39*x^4 - 22*x^5 + 7*x^6 - x^7) / (1 - x)^9.
a(n) = (40320 + 79344*n + 64140*n^2 + 37884*n^3 + 16009*n^4 + 3696*n^5 + 490*n^6 + 36*n^7 + n^8) / 40320.
(End)
EXAMPLE
Some solutions for 3 X 2:
..0..1....1..2....0..2....0..1....0..0....0..1....0..0....0..2....0..1....0..2
..0..1....2..0....1..1....0..2....0..2....1..2....0..0....2..1....1..2....2..1
..2..2....2..1....1..2....2..2....0..2....2..2....0..2....2..1....2..0....2..2
CROSSREFS
Cf. A184137.
Sequence in context: A100874 A047923 A006816 * A326805 A061648 A281050
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 09 2011
STATUS
approved

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Last modified September 19 21:59 EDT 2024. Contains 376015 sequences. (Running on oeis4.)