This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A161474 #15 Sep 08 2022 08:45:45 %S A161474 1,1,1,3,4,5,18,28,40,162,280,440,1944,3640,6160,29160,58240,104720, %T A161474 524880,1106560,2094400,11022480,24344320,48171200,264539520, %U A161474 608608000,1252451200,7142567040,17041024000,36321084800,214277011200,528271744000,1162274713600 %N A161474 Triple factorials n!!!: a(n) = n*a(n-3). %C A161474 This definition of triple factorials starts with a(1)=a(2)=1. The main version is A007661. %H A161474 Wikipedia, <a href="http://en.wikipedia.org/wiki/Factorial#Multifactorials">Multifactorials</a> %p A161474 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 %t A161474 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 *) %o A161474 (Magma) TripleFactorial:=func<n | &*[n..3 by -3]>; [TripleFactorial(n): n in [1..35]]; // _Vincenzo Librandi_, Apr 08 2016 %Y A161474 Cf. A002110, A006882, A001813. %K A161474 nonn %O A161474 0,4 %A A161474 Asbel Torres da Cunha (asbeltc(AT)gmail.com), Jun 11 2009 %E A161474 Corrected and extended by _R. J. Mathar_, Jun 16 2009 %E A161474 a(0)=1 prepended by _Alois P. Heinz_, May 06 2020