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A201722 Number of n X 1 0..4 arrays with rows and columns lexicographically nondecreasing and no element equal to the number of horizontal and vertical neighbors equal to itself. 1
4, 10, 20, 35, 56, 83, 116, 155, 200, 251, 308, 371, 440, 515, 596, 683, 776, 875, 980, 1091, 1208, 1331, 1460, 1595, 1736, 1883, 2036, 2195, 2360, 2531, 2708, 2891, 3080, 3275, 3476, 3683, 3896, 4115, 4340, 4571, 4808, 5051, 5300, 5555, 5816, 6083, 6356 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Column 1 of A201729.
LINKS
FORMULA
Empirical: a(n) = 3*n^2 - 6*n + 11 for n>2.
Conjectures from Colin Barker, May 23 2018: (Start)
G.f.: x*(4 - 2*x + 2*x^2 + x^3 + x^4) / (1 - x)^3.
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>5.
(End)
EXAMPLE
Some solutions for n=8.
..0....3....1....0....0....0....0....1....0....0....0....0....0....0....0....0
..0....3....3....0....0....0....0....3....0....0....0....0....0....0....0....0
..0....3....3....0....0....0....0....3....0....2....0....2....0....0....0....0
..1....3....3....0....0....4....1....3....0....3....0....3....1....1....0....3
..2....4....3....0....2....4....2....4....0....3....2....4....4....2....4....4
..4....4....3....2....3....4....3....4....3....3....3....4....4....2....4....4
..4....4....4....2....3....4....3....4....4....3....3....4....4....3....4....4
..4....4....4....3....3....4....4....4....4....3....4....4....4....3....4....4
CROSSREFS
Cf. A201729.
Sequence in context: A038409 A374710 A347252 * A352208 A341193 A090579
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 04 2011
STATUS
approved

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Last modified July 20 05:10 EDT 2024. Contains 374441 sequences. (Running on oeis4.)