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A240187
Number of n X 2 0..3 arrays with no element equal to zero plus the sum of elements to its left or one plus the sum of elements above it or three plus the sum of the elements diagonally to its northwest, modulo 4.
1
1, 5, 12, 27, 73, 154, 358, 872, 1871, 4438, 10338, 22880, 54100, 123711, 279854, 655190, 1491102, 3413413, 7919449, 18045604, 41514375, 95741087, 218782546, 503899032, 1158409848, 2653808377, 6109601340, 14027233372, 32187863462
OFFSET
1,2
LINKS
FORMULA
Empirical: a(n) = 2*a(n-2) + 10*a(n-3) - a(n-4) - 5*a(n-5) - 15*a(n-6) + a(n-7) + 4*a(n-8) + 2*a(n-9) + 10*a(n-10) + 5*a(n-11) - 6*a(n-13).
Empirical g.f.: x*(1 + 5*x + 10*x^2 + 7*x^3 - 10*x^5 - 6*x^6 - 5*x^7 - 6*x^8 + 4*x^9 + 4*x^10 + 6*x^11) / (1 - 2*x^2 - 10*x^3 + x^4 + 5*x^5 + 15*x^6 - x^7 - 4*x^8 - 2*x^9 - 10*x^10 - 5*x^11 + 6*x^13). - Colin Barker, Oct 27 2018
EXAMPLE
Some solutions for n=4:
..2..0....2..0....2..0....2..0....2..0....2..0....2..0....2..0....2..0....2..0
..1..0....1..0....1..3....2..0....2..0....1..3....1..3....2..0....2..3....1..3
..2..3....2..3....1..2....2..0....2..3....2..1....2..3....2..0....2..3....2..3
..1..2....1..3....2..3....1..0....2..3....1..2....1..0....2..0....1..0....1..2
CROSSREFS
Column 2 of A240192.
Sequence in context: A357417 A229422 A128439 * A172426 A145768 A162778
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 02 2014
STATUS
approved