The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A123144 a(n) = if mod[n, 3] - 1 == 0 then a(n - 1) else n*a(n - 1). 1
 1, 2, 6, 6, 30, 180, 180, 1440, 12960, 12960, 142560, 1710720, 1710720, 23950080, 359251200, 359251200, 6107270400, 109930867200, 109930867200, 2198617344000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Without duplicates this sequence is {1, 2, 8, 48, 384, 3840, 46080, 645120, ...} LINKS Harvey P. Dale, Table of n, a(n) for n = 1..632 MATHEMATICA 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}] nxt[{n_, a_}]:={n+1, If[Mod[n+1, 3]==1, a, a(n+1)]}; Transpose[NestList[nxt, {1, 1}, 20]][[2]] (* Harvey P. Dale, Jul 22 2014 *) CROSSREFS Cf. A007559. Sequence in context: A093364 A113461 A061558 * A179215 A069260 A056603 Adjacent sequences:  A123141 A123142 A123143 * A123145 A123146 A123147 KEYWORD nonn AUTHOR Roger L. Bagula, Oct 01 2006 EXTENSIONS Edited by N. J. A. Sloane, Oct 04 2006 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 2 14:21 EDT 2020. Contains 334787 sequences. (Running on oeis4.)