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A161474
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Triple factorials n!!!: a(n) = n*a(n-3).
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3
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1, 1, 1, 3, 4, 5, 18, 28, 40, 162, 280, 440, 1944, 3640, 6160, 29160, 58240, 104720, 524880, 1106560, 2094400, 11022480, 24344320, 48171200, 264539520, 608608000, 1252451200, 7142567040, 17041024000, 36321084800, 214277011200, 528271744000, 1162274713600
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OFFSET
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0,4
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COMMENTS
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This definition of triple factorials starts with a(1)=a(2)=1. The main version is A007661.
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LINKS
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Table of n, a(n) for n=0..32.
Wikipedia, Multifactorials
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MAPLE
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A161474 := proc(n) if n < 3 then 1 ; else procname(n-3)*n ; fi; end: seq(A161474(n), n=0..80) ; # R. J. Mathar, Jun 16 2009
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MATHEMATICA
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multiFactorialRev[n_, k_] := If[n < k, 1, If[n >= k, n*multiFactorialRev[n - k, k]]]; Array[ multiFactorialRev[#, 3] &, 32] (* Robert G. Wilson v, Aug 29 2012 *)
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PROG
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(MAGMA) TripleFactorial:=func<n | &*[n..3 by -3]>; [TripleFactorial(n): n in [1..35]]; // Vincenzo Librandi, Apr 08 2016
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CROSSREFS
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Cf. A002110, A006882, A001813.
Sequence in context: A249541 A059184 A161961 * A247573 A084930 A114336
Adjacent sequences: A161471 A161472 A161473 * A161475 A161476 A161477
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KEYWORD
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nonn
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AUTHOR
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Asbel Torres da Cunha (asbeltc(AT)gmail.com), Jun 11 2009
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EXTENSIONS
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Corrected and extended by R. J. Mathar, Jun 16 2009
a(0)=1 prepended by Alois P. Heinz, May 06 2020
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STATUS
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approved
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