This site is supported by donations to The OEIS Foundation.

 Annual Appeal: Please make a donation to keep the OEIS running. In 2018 we replaced the server with a faster one, added 20000 new sequences, and reached 7000 citations (often saying "discovered thanks to the OEIS"). Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A169638 Number of multiset permutations of the n initial elements of A005229 with additional element A005229(0)=1. 1
 1, 1, 1, 4, 20, 60, 420, 3360, 30240, 151200, 1663200, 9979200, 129729600, 1816214400, 27243216000, 217945728000, 3705077376000, 66691392768000, 633568231296000, 12671364625920000, 266098657144320000, 5854170457175040000, 134645920515025920000, 1615751046180311040000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 LINKS Robert Israel, Table of n, a(n) for n = 0..429 FORMULA a(n) = number of permutations of the list b[0..n] where b(0)=0 and b(n) = A005229(n) for n>=1. MAPLE N:= 100: # to get a(0) to a(N) A005229:= proc(n) option remember; procname(procname(n-2))+procname(n-procname(n-2)) end proc: A005229(1):= 1: A005229(2):= 1: V:= Vector(N): A[0]:= 1: V[1]:= 1: for n from 1 to N do   r:= A005229(n);   V[r]:= V[r]+1;   A[n]:= A[n-1]*(n+1)/V[r]; od: seq(A[i], i=0..N); # Robert Israel, Dec 23 2014 MATHEMATICA Mallows[n_Integer?Positive] := Mallows[n] = Mallows[Mallows[n - 2]] + Mallows[ n - Mallows[n - 2]]; Mallows[0] = Mallows[1] = Mallows[2] = 1; a[m_] := Length[Permutations[Table[Mallows[i], {i, 0, m}]]]; Table[a[m], {m, 0, 10}] (* A much better way to compute the terms is to use the multinomials of the multiplicities of the terms of A005229! - Joerg Arndt, Dec 23 2014 *) CROSSREFS Cf. A169637. Sequence in context: A135507 A197404 A169637 * A226424 A225260 A131479 Adjacent sequences:  A169635 A169636 A169637 * A169639 A169640 A169641 KEYWORD nonn AUTHOR Roger L. Bagula, Apr 04 2010 EXTENSIONS Edited and new name, Joerg Arndt, Dec 23 2014 a(11) to a(23) from Robert Israel, Dec 23 2014 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 December 18 16:19 EST 2018. Contains 318229 sequences. (Running on oeis4.)