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A264507
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Number of (1+1) X (n+1) arrays of permutations of 0..n*2+1 with each element having directed index change -1,1 0,-1 0,1 or 1,0.
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1
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1, 1, 3, 6, 12, 24, 46, 91, 177, 349, 684, 1345, 2640, 5185, 10180, 19989, 39249, 77067, 151326, 297136, 583444, 1145622, 2249491, 4416993, 8673001, 17029896, 33439105, 65659456, 128925825, 253152696, 497078745, 976040481, 1916507251, 3763163638
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OFFSET
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1,3
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LINKS
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FORMULA
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Empirical: a(n) = 2*a(n-1) + a(n-2) - 3*a(n-3) + a(n-4) + 2*a(n-5) - a(n-6).
Empirical g.f.: x*(1 - x + 2*x^3 - x^4) / (1 - 2*x - x^2 + 3*x^3 - x^4 - 2*x^5 + x^6). - Colin Barker, Jan 08 2019
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EXAMPLE
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Some solutions for n=4:
..1..2..3..7..8....1..5..3..2..8....1..5..6..2..3....1..5..6..4..3
..0..5..6..9..4....0..7..6..9..4....0..7..8..9..4....0..7..2..9..8
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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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