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A240001
Number of 2 X n 0..3 arrays with no element equal to one 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
5, 13, 25, 42, 65, 95, 133, 180, 237, 305, 385, 478, 585, 707, 845, 1000, 1173, 1365, 1577, 1810, 2065, 2343, 2645, 2972, 3325, 3705, 4113, 4550, 5017, 5515, 6045, 6608, 7205, 7837, 8505, 9210, 9953, 10735, 11557, 12420, 13325, 14273, 15265, 16302
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = (1/6)*n^3 + 1*n^2 + (23/6)*n.
Conjectures from Colin Barker, Oct 27 2018: (Start)
G.f.: x*(5 - 7*x + 3*x^2) / (1 - x)^4.
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n>4.
(End)
EXAMPLE
Some solutions for n=5:
..0..0..0..0..0....0..0..3..3..0....0..0..0..0..3....0..0..0..0..0
..3..3..0..0..0....0..0..3..2..3....0..0..0..3..3....0..0..0..0..3
CROSSREFS
Row 2 of A240000.
Sequence in context: A146875 A241233 A064276 * A301685 A102724 A147031
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 30 2014
STATUS
approved