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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

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

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: A138778 A301244 A038409 * A090579 A276643 A000292

Adjacent sequences:  A201719 A201720 A201721 * A201723 A201724 A201725

KEYWORD

nonn

AUTHOR

R. H. Hardin, Dec 04 2011

STATUS

approved

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Last modified August 16 23:58 EDT 2018. Contains 313809 sequences. (Running on oeis4.)