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A108188
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a(n) = (n-1)*(a(n-1)+a(n-2)+a(n-3)).
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0
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0, 1, 1, 6, 32, 195, 1398, 11375, 103744, 1048653, 11637720, 140691287, 1840531920, 25907192051, 390437813612, 6272783063745, 107026049110528, 1932717589794045, 36828295595429724, 738492745452351643
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OFFSET
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1,4
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COMMENTS
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LINKS
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MATHEMATICA
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F[1] = 0; F[2] = 1; F[3] = 1; F[n__] := F[n] = (n - 1)*(F[n - 1] + F[n - 2] + F[n - 3]) a = Table[F[n], {n, 1, 25}]
RecurrenceTable[{a[1]==0, a[2]==a[3]==1, a[n]==(n-1)(a[n-1]+a[n-2]+a[n-3])}, a, {n, 20}] (* Harvey P. Dale, Oct 26 2019 *)
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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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