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A238806 Number of n X 2 0..2 arrays with no element equal to one plus the sum of elements to its left or one plus the sum of the sum of elements above it, modulo 3. 1
3, 8, 15, 25, 39, 58, 83, 115, 155, 204, 263, 333, 415, 510, 619, 743, 883, 1040, 1215, 1409, 1623, 1858, 2115, 2395, 2699, 3028, 3383, 3765, 4175, 4614, 5083, 5583, 6115, 6680, 7279, 7913, 8583, 9290, 10035, 10819, 11643, 12508, 13415, 14365, 15359 (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) = (1/6)*n^3 + (23/6)*n - 1.

Conjectures from Colin Barker, Oct 24 2018: (Start)

G.f.: (3 - 4*x + x^2 + x^3) / (1 - x)^4.

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

(End)

EXAMPLE

Some solutions for n=5:

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

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

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

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

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

CROSSREFS

Column 2 of A238812.

Sequence in context: A274696 A022451 A212772 * A080181 A071399 A001208

Adjacent sequences:  A238803 A238804 A238805 * A238807 A238808 A238809

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 05 2014

STATUS

approved

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Last modified June 24 20:32 EDT 2022. Contains 354830 sequences. (Running on oeis4.)