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A190918
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Number of permutations of n copies of 1..4 introduced in order 1..4 with no element equal to another within a distance of 1
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8
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1, 36, 1721, 94376, 5609649, 351574834, 22875971289, 1530622143864, 104650147201049, 7279277647839552, 513492654638478897, 36647810215955194122, 2641438793287744496337, 191996676519223794534702
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OFFSET
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1,2
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LINKS
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FORMULA
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Conjecture: n^3 *(n-1) *(2*n+1) *(5*n-7) *a(n) -2*(n-1) *(415*n^5 -1026*n^4 +727*n^3 -90*n^2 -98*n +36)*a(n-1) +(1630*n^4 -6387*n^3 +7388*n^2 +111*n -3510) *(n-2)^2 *a(n-2) -162*(3+5*n) *(n-2)^2 *(n-3)^3 *a(n-3)=0. - R. J. Mathar, Nov 01 2015
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EXAMPLE
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Some solutions for n=2
..1....1....1....1....1....1....1....1....1....1....1....1....1....1....1....1
..2....2....2....2....2....2....2....2....2....2....2....2....2....2....2....2
..3....3....3....3....3....3....3....1....3....3....1....3....3....3....1....3
..4....1....4....2....4....1....2....3....4....4....3....4....1....2....2....4
..2....4....1....4....1....4....4....4....2....2....4....3....4....4....3....2
..4....2....2....3....3....2....1....3....3....1....2....1....3....1....4....4
..3....3....4....1....4....4....3....4....4....4....3....4....4....4....3....1
..1....4....3....4....2....3....4....2....1....3....4....2....2....3....4....3
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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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