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A252924

Number of n X 2 nonnegative integer arrays with upper left 0 and lower right n+2-6 and value increasing by 0 or 1 with every step right or down.

0, 0, 0, 1, 19, 120, 483, 1500, 3923, 9069, 19095, 37356, 68860, 120835, 203424, 330525, 520794, 798830, 1196562, 1754859, 2525385, 3572722, 4976785, 6835554, 9268149, 12418275, 16458065, 21592350, 28063386, 36156069, 46203670, 58594123

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OFFSET

1,5

COMMENTS

Column 2 of A252930.

LINKS

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

FORMULA

Empirical: a(n) = (1/40320)*n^8 + (1/1120)*n^7 + (7/2880)*n^6 - (1/16)*n^5 + (647/5760)*n^4 + (87/160)*n^3 - (21317/10080)*n^2 + (141/56)*n - 1.

Empirical: G.f.: x^4*(-1-10*x+15*x^2-3*x^3-3*x^4+x^5) / (x-1)^9 . - R. J. Mathar, Nov 21 2015

EXAMPLE

Some solutions for n=6:

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

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

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

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

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

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

CROSSREFS

Sequence in context: A044732 A159851 A221372 * A157340 A252054 A070302

Adjacent sequences: A252921 A252922 A252923 * A252925 A252926 A252927

KEYWORD

nonn

AUTHOR

R. H. Hardin, Dec 24 2014

STATUS

approved