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A264280
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Number of (n+1) X (3+1) arrays of permutations of 0..n*4+3 with each element having directed index change 0,0 0,1 1,0 or -1,-2.
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1
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8, 32, 132, 556, 2324, 9724, 40692, 170268, 712468, 2981244, 12474676, 52198876, 218420308, 913955132, 3824342132, 16002528156, 66960773524, 280189801724, 1172422611892, 4905870136668, 20528060064468, 85897351187644
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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) = 3*a(n-1) +4*a(n-2) +4*a(n-3).
Empirical g.f.: 4*x*(2 + 2*x + x^2) / (1 - 3*x - 4*x^2 - 4*x^3). - Colin Barker, Jan 07 2019
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EXAMPLE
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Some solutions for n=4:
..0..1..2..3....0..1..2..3....6..0..1..3....0..7..2..3....0..1..2..3
..4.11..5..6....4.11..6..7....4.11..2..7....4..1..5..6....4..5..6..7
..8..9.10..7...14..5..9.10...14..5..9.10....8.15..9.11....8..9.10.11
.12.19.14.15....8.19.13.15....8.19.13.15...18.13.10.14...12.19.13.14
.16.13.17.18...12.16.17.18...12.16.17.18...12.16.17.19...16.17.18.15
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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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