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A291129
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Number of defective parking functions of length n and defect three.
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2
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1, 46, 1442, 41070, 1166083, 34268902, 1059688652, 34723442062, 1208687001381, 44701813604150, 1754724115372438, 72987949807322222, 3210789166789472775, 149073947870611952326, 7289995971215959818304, 374726414201304528649678, 20207920615298454956444905
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OFFSET
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4,2
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LINKS
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FORMULA
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a(n) ~ (-13*exp(1)/6 + 14*exp(2) - 15*exp(3) + 4*exp(4)) * n^(n-1). - Vaclav Kotesovec, Aug 19 2017
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MAPLE
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S:= (n, k)-> add(binomial(n, i)*k*(k+i)^(i-1)*(n-k-i)^(n-i), i=0..n-k):
a:= n-> S(n, 3)-S(n, 4):
seq(a(n), n=4..23);
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MATHEMATICA
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S[n_, k_] := Sum[Binomial[n, i]*k*(k+i)^(i-1)*(n-k-i)^(n-i), {i, 0, n-k}];
a[n_] := S[n, 3] - S[n, 4];
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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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