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A239987
Number of 3 X n 0..3 arrays with no element equal to zero plus the sum of elements to its left or two plus the sum of the elements above it or one plus the sum of the elements diagonally to its northwest, modulo 4.
1
3, 6, 13, 22, 38, 65, 107, 169, 257, 378, 540, 752, 1024, 1367, 1793, 2315, 2947, 3704, 4602, 5658, 6890, 8317, 9959, 11837, 13973, 16390, 19112, 22164, 25572, 29363, 33565, 38207, 43319, 48932, 55078, 61790, 69102, 77049, 85667, 94993, 105065
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = (1/24)*n^4 - (1/4)*n^3 + (71/24)*n^2 - (43/4)*n + 23 for n>3.
Conjectures from Colin Barker, Oct 27 2018: (Start)
G.f.: x*(3 - 9*x + 13*x^2 - 13*x^3 + 13*x^4 - 8*x^5 + x^6 + x^7) / (1 - x)^5.
a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n>8.
(End)
EXAMPLE
Some solutions for n=4:
..3..0..0..0....3..0..0..0....3..0..0..0....3..0..0..0....3..0..0..0
..2..3..0..3....2..1..0..0....3..1..3..0....3..1..3..0....2..1..0..0
..2..0..1..0....2..0..0..0....3..2..3..1....3..1..2..3....2..0..3..3
CROSSREFS
Row 3 of A239986.
Sequence in context: A178097 A361276 A211870 * A048134 A058397 A174369
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 30 2014
STATUS
approved