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A269538
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Number of length-4 0..n arrays with no repeated value differing from the previous repeated value by other than one.
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1
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10, 64, 222, 568, 1210, 2280, 3934, 6352, 9738, 14320, 20350, 28104, 37882, 50008, 64830, 82720, 104074, 129312, 158878, 193240, 232890, 278344, 330142, 388848, 455050, 529360, 612414, 704872, 807418, 920760, 1045630, 1182784, 1333002
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OFFSET
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1,1
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LINKS
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FORMULA
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Empirical: a(n) = n^4 + 4*n^3 + 3*n^2 + 2*n.
G.f.: 2*x*(1 + x)*(5 + 2*x - x^2) / (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>5.
(End)
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EXAMPLE
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Some solutions for n=3:
..3. .0. .1. .3. .2. .3. .2. .1. .2. .1. .1. .0. .1. .1. .3. .3
..1. .3. .3. .3. .1. .0. .0. .3. .2. .2. .2. .2. .2. .1. .3. .1
..3. .2. .0. .2. .2. .1. .1. .1. .3. .3. .0. .2. .0. .3. .0. .3
..1. .3. .0. .0. .3. .0. .3. .0. .0. .3. .2. .1. .0. .0. .1. .2
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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