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A240290
Number of n X 2 0..3 arrays with no element equal to zero plus the sum of elements to its left or two plus the sum of elements above it or two plus the sum of the elements diagonally to its northwest, modulo 4.
1
4, 6, 24, 56, 230, 552, 2270, 5456, 22416, 53864, 221258, 531640, 2183802, 5247248, 21554008, 51790104, 212737190, 511166312, 2099707822, 5045191696, 20724034720, 49795846120, 204545417674, 491483066744, 2018855326250, 4850918775632
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 12*a(n-2) - 24*a(n-4) + 31*a(n-6) - 16*a(n-8) for n>9.
Empirical g.f.: 2*x*(1 - x)*(2 + 5*x - 7*x^2 - 15*x^3 + 4*x^4 + 16*x^5 - 3*x^6 - 8*x^7) / (1 - 12*x^2 + 24*x^4 - 31*x^6 + 16*x^8). - Colin Barker, Oct 27 2018
EXAMPLE
Some solutions for n=4:
..3..0....1..3....1..3....3..1....3..1....1..3....1..3....1..3....3..0....3..1
..3..0....1..2....1..0....3..2....3..0....1..0....1..2....1..2....3..0....3..2
..3..0....1..0....3..0....1..3....1..0....3..2....3..2....3..0....1..3....1..2
..1..3....3..1....1..3....3..2....3..2....1..0....1..2....1..2....3..2....3..2
CROSSREFS
Column 2 of A240295.
Sequence in context: A122174 A283185 A034458 * A067001 A057343 A377117
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 03 2014
STATUS
approved