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A014508
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a(n) = floor( n! / e ).
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2
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0, 0, 2, 8, 44, 264, 1854, 14832, 133496, 1334960, 14684570, 176214840, 2290792932, 32071101048, 481066515734, 7697064251744, 130850092279664, 2355301661033952, 44750731559645106, 895014631192902120
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OFFSET
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1,3
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LINKS
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FORMULA
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E.g.f.: -exp(x)/2-(x+1)*exp(-x)/(2*x-2). - Mark van Hoeij, Oct 30 2011
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MATHEMATICA
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f[n_] := Floor[n!/E]; Array[f, 20] (* or *) a[0] = 1; a[n_] := a[n] = n*a[n - 1] + (-1)^n; f[n_] := Sum[(n - k - 1) a[n - k - 1], {k, 0, n - 1}]; Array[f, 20] (* Robert G. Wilson v, Apr 01 2011 *)
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PROG
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(PARI) vector(30, n, if(n, round(n!/exp(1)), 1)-(n+1)%2) \\ Altug Alkan, Nov 04 2015
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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