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A240316
Number of n X 2 0..3 arrays with no element equal to two plus the sum of elements to its left or two plus the sum of elements above it or zero plus the sum of the elements diagonally to its northwest, modulo 4.
1
2, 4, 18, 44, 184, 444, 1826, 4388, 18022, 43300, 177856, 427348, 1755406, 4217900, 17325794, 41630540, 171004968, 410891868, 1687812450, 4055486788, 16658643286, 40027496964, 164420161936, 395069839924, 1622820610830, 3899323972492
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 12*a(n-2) - 24*a(n-4) + 31*a(n-6) - 16*a(n-8).
Empirical g.f.: 2*x*(1 + 2*x - 3*x^2 - 2*x^3 + 8*x^4 + 6*x^5 - 6*x^6 - 4*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..3....1..1....1..1....1..1....3..3....1..1....1..1....1..1....3..3....1..1
..3..0....1..2....1..0....1..0....3..2....1..0....1..2....1..2....3..2....1..0
..3..0....1..2....3..2....1..0....1..1....1..0....3..2....3..2....3..0....3..0
..1..2....3..0....1..2....3..0....3..3....3..2....1..1....1..2....1..0....1..2
CROSSREFS
Column 2 of A240321.
Sequence in context: A143533 A064723 A301620 * A151449 A045664 A106520
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 03 2014
STATUS
approved