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 A169638 Number of multiset permutations of the n initial elements of A005229 with additional element A005229(0)=1. 2
 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: A355990 A169637 A356012 * 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

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Last modified May 23 18:59 EDT 2024. Contains 372765 sequences. (Running on oeis4.)