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A240333
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 one plus the sum of the elements diagonally to its northwest, modulo 4.
1
4, 15, 48, 125, 284, 582, 1097, 1932, 3219, 5123, 7846, 11631, 16766, 23588, 32487, 43910, 58365, 76425, 98732, 126001, 159024, 198674, 245909, 301776, 367415, 444063, 533058, 635843, 753970, 889104, 1043027, 1217642, 1414977, 1637189
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = (1/30)*n^5 + (1/24)*n^4 + (23/12)*n^3 - (193/24)*n^2 + (581/20)*n - 30 for n>2.
Conjectures from Colin Barker, Oct 27 2018: (Start)
G.f.: x*(4 - 9*x + 18*x^2 - 18*x^3 + 14*x^4 - 6*x^5 - x^6 + 2*x^7) / (1 - x)^6.
a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6) for n>8.
(End)
EXAMPLE
Some solutions for n=4:
..0..0....0..3....0..3....3..3....3..0....0..0....0..3....0..3....0..3....0..3
..3..3....0..0....0..3....0..3....0..3....3..0....3..2....3..3....3..3....0..0
..3..2....3..3....3..2....3..3....3..3....0..3....3..2....3..3....0..3....3..0
..3..2....0..3....0..3....3..2....3..3....0..0....3..3....3..2....0..0....3..2
CROSSREFS
Column 2 of A240338.
Sequence in context: A307075 A219903 A238807 * A227099 A225976 A093967
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 04 2014
STATUS
approved