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A229449 Number of 6 X n 0..2 arrays with horizontal differences mod 3 never 1, vertical differences mod 3 never -1, and rows and columns lexicographically nondecreasing. 1
23, 84, 293, 915, 2546, 6374, 14536, 30571, 59969, 110816, 194535, 326723, 528084, 825458, 1252946, 1853131, 2678395, 3792332, 5271257, 7205811, 9702662, 12886302, 16900940, 21912491, 28110661, 35711128, 44957819, 56125283, 69521160, 85488746 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

FORMULA

Empirical: a(n) = (2/15)*n^6 - (5/8)*n^5 + (9/2)*n^4 - (55/8)*n^3 + (283/15)*n^2 - 4*n + 11.

Conjectures from Colin Barker, Sep 17 2018: (Start)

G.f.: x*(23 - 77*x + 188*x^2 - 177*x^3 + 159*x^4 - 31*x^5 + 11*x^6) / (1 - x)^7.

a(n) = 7*a(n-1) - 21*a(n-2) + 35*a(n-3) - 35*a(n-4) + 21*a(n-5) - 7*a(n-6) + a(n-7) for n>7.

(End)

EXAMPLE

Some solutions for n=4.

..0..0..0..0....0..2..2..2....0..2..2..2....0..2..2..2....0..2..2..2

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

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

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

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

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

CROSSREFS

Row 6 of A229445.

Sequence in context: A262119 A104068 A304839 * A060456 A056580 A010011

Adjacent sequences:  A229446 A229447 A229448 * A229450 A229451 A229452

KEYWORD

nonn

AUTHOR

R. H. Hardin, Sep 23 2013

STATUS

approved

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Last modified June 16 21:55 EDT 2021. Contains 345080 sequences. (Running on oeis4.)