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A264631
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Number of (4+1)X(n+1) arrays of permutations of 0..n*5+4 with each element having directed index change -2,0 -1,0 0,-1 or 1,1.
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1
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1, 8, 22, 108, 684, 2736, 13556, 68972, 316068, 1534532, 7430832, 35311040, 170094764, 817176616, 3914397580, 18804795120, 90252696296, 433011737840, 2078662232124, 9975949817428, 47876003240128, 229786823307824
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OFFSET
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1,2
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 3*a(n-1) +36*a(n-3) -18*a(n-4) +186*a(n-5) +83*a(n-6) +144*a(n-7) +684*a(n-8) -1872*a(n-9) +508*a(n-10) -5048*a(n-11) -3240*a(n-12) +720*a(n-13) -95040*a(n-14) +3072*a(n-15) +3456*a(n-16) +13824*a(n-18) for n>21
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EXAMPLE
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Some solutions for n=4
..1.11..7..4..9....1..6..3..4..9....1..2..3..4.14....1..2.12..4.14
..6..0.12..2..3...10..0..8..2.14...15..0.17..9.19....6..0..8..9..3
.20..5.13.14..8...20..5.22..7.19...20..5..6..7..8...15..5.13..7.19
.16.10.22.19.24...16.17.11.12.13...16.10.11.12.13...20.10.11.23.24
.21.15.23.17.18...21.15.23.24.18...21.22.23.24.18...21.22.16.17.18
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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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