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A229795
Number of 2 X 2 0..n arrays with rows and columns in lexicographically nondecreasing order.
1
7, 29, 86, 205, 421, 777, 1324, 2121, 3235, 4741, 6722, 9269, 12481, 16465, 21336, 27217, 34239, 42541, 52270, 63581, 76637, 91609, 108676, 128025, 149851, 174357, 201754, 232261, 266105, 303521, 344752, 390049, 439671, 493885, 552966, 617197
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = (1/3)*n^4 + (7/6)*n^3 + (13/6)*n^2 + (7/3)*n + 1.
Conjectures from Colin Barker, Sep 21 2018: (Start)
G.f.: x*(7 - 6*x + 11*x^2 - 5*x^3 + x^4) / (1 - x)^5.
a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n>5.
(End)
EXAMPLE
Some solutions for n=2:
..0..2....1..2....1..1....1..2....0..1....0..0....0..2....1..2....0..0....0..2
..1..0....2..2....1..1....2..1....1..0....2..2....0..2....2..0....0..1....2..2
CROSSREFS
Row 2 of A229794.
Sequence in context: A375656 A079796 A242727 * A114043 A331767 A166189
KEYWORD
nonn
AUTHOR
R. H. Hardin, Sep 29 2013
STATUS
approved