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Search: id:A123144
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| A123144 |
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a(n) = if mod[n, 3] - 1 == 0 then a(n - 1) else n*a(n - 1). |
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+0
1
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| 1, 2, 6, 6, 30, 180, 180, 1440, 12960, 12960, 142560, 1710720, 1710720, 23950080, 359251200, 359251200, 6107270400, 109930867200, 109930867200, 2198617344000
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OFFSET
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1,2
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COMMENT
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Without duplicates this sequence is {1, 2, 8, 48, 384, 3840, 46080, 645120, ...}
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MATHEMATICA
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f[1]=1; f[n_] := f[n] = If[Mod[n, 3] - 1 == 0, f[n - 1], n*f[n - 1]] a = Table[f[n], {n, 1, 20}]
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CROSSREFS
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Cf. A007559.
Sequence in context: A093364 A113461 A061558 this_sequence A069260 A056603 A019198
Adjacent sequences: A123141 A123142 A123143 this_sequence A123145 A123146 A123147
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KEYWORD
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nonn
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AUTHOR
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Roger Bagula (rlbagulatftn(AT)yahoo.com), Oct 01 2006
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EXTENSIONS
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Edited by N. J. A. Sloane (njas(AT)research.att.com), Oct 04 2006
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