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A238807 Number of n X 3 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
4, 15, 48, 118, 254, 498, 916, 1605, 2702, 4395, 6936, 10656, 15982, 23456, 33756, 47719, 66366, 90929, 122880, 163962, 216222, 282046, 364196, 465849, 590638, 742695, 926696, 1147908, 1412238, 1726284, 2097388, 2533691, 3044190, 3638797 (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) = (1/360)*n^6 - (1/30)*n^5 + (7/9)*n^4 - (65/12)*n^3 + (11959/360)*n^2 - (1631/20)*n + 83 for n>2.

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

G.f.: x*(4 - 13*x + 27*x^2 - 43*x^3 + 51*x^4 - 41*x^5 + 27*x^6 - 16*x^7 + 6*x^8) / (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>9.

(End)

EXAMPLE

Some solutions for n=5:

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

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

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

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

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

CROSSREFS

Column 3 of A238812.

Sequence in context: A173414 A307075 A219903 * A240333 A227099 A225976

Adjacent sequences:  A238804 A238805 A238806 * A238808 A238809 A238810

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 05 2014

STATUS

approved

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Last modified January 23 19:17 EST 2022. Contains 350515 sequences. (Running on oeis4.)