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A229450 Number of 7 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
30, 142, 625, 2402, 8024, 23610, 62205, 149031, 329106, 677706, 1314145, 2419348, 4257692, 7203590, 11773293, 18662385, 28789446, 43346358, 63855729, 92235910, 130874080, 182707874, 251316029, 341018523, 456986682, 605363730, 793396257 (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) = (95/1008)*n^7 - (241/360)*n^6 + (232/45)*n^5 - (1061/72)*n^4 + (5771/144)*n^3 - (7217/180)*n^2 + (18133/420)*n - 3.

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

G.f.: x*(30 - 98*x + 329*x^2 - 302*x^3 + 456*x^4 - 66*x^5 + 123*x^6 + 3*x^7) / (1 - x)^8.

a(n) = 8*a(n-1) - 28*a(n-2) + 56*a(n-3) - 70*a(n-4) + 56*a(n-5) - 28*a(n-6) + 8*a(n-7) - a(n-8) for n>8.

(End)

EXAMPLE

Some solutions for n=4:

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

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

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

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

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

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

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

CROSSREFS

Row 7 of A229445.

Sequence in context: A064495 A267904 A218407 * A124958 A126417 A135175

Adjacent sequences:  A229447 A229448 A229449 * A229451 A229452 A229453

KEYWORD

nonn

AUTHOR

R. H. Hardin, Sep 23 2013

STATUS

approved

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Last modified November 13 07:13 EST 2019. Contains 329085 sequences. (Running on oeis4.)