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A284204
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Eighth column of Euler's difference table in A068106.
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1
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0, 0, 0, 0, 0, 0, 5040, 35280, 287280, 2656080, 27422640, 312273360, 3884393520, 52370755920, 760381337520, 11824686110160, 196038409800240, 3450899827705680, 64272619406504880, 1262590566656060880, 26087355385405781040, 565510731026706254160
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OFFSET
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1,7
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COMMENTS
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For n >= 8, this is the number of permutations of [n] that avoid substrings j(j+7), 1 <= j <= n-7.
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LINKS
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FORMULA
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For n>=8: a(n) = Sum_{j=0..n-7} (-1)^j*binomial(n-7,j)*(n-j)!.
Note a(n)/n! ~ 1/e.
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EXAMPLE
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a(11)=27422640 since this is the number of permutations in S11 that avoid substrings {18,29,3(10),4(11)}.
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MATHEMATICA
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With[{k = 8}, ConstantArray[0, k - 2]~Join~Table[Sum[(-1)^j*Binomial[n - (k - 1), j] (n - j)!, {j, 0, n - (k - 1)}], {n, k - 1, k + 12}]] (* Michael De Vlieger, Mar 26 2017 *)
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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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