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A007714
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Number of 5-level rooted trees with n leaves.
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6
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1, 1, 5, 15, 55, 170, 571, 1789, 5727, 17836, 55627, 171169, 524879, 1595896, 4829894, 14527981, 43497312, 129588391, 384430264, 1135607519, 3341662498, 9796626673, 28620419254, 83334382425, 241879403752, 699937499318, 2019607806247, 5811320364410, 16677611788799
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OFFSET
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0,3
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LINKS
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B. A. Huberman and T. Hogg, Complexity and adaptation, Evolution, games and learning (Los Alamos, N.M., 1985). Phys. D 22 (1986), no. 1-3, 376-384.
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FORMULA
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Euler transform applied 4 times to all-1's sequence.
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MAPLE
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with(numtheory): etr:= proc(p) local b; b:=proc(n) option remember; local d, j; if n=0 then 1 else add(add(d*p(d), d=divisors(j)) *b(n-j), j=1..n)/n fi end end: b[0]:= etr(1): for k from 1 to 2 do b[k]:= etr(b[k-1]) od: a:= etr(b[2]): seq(a(n), n=0..25); # Alois P. Heinz, Sep 08 2008
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MATHEMATICA
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i[ n_, m_ ] := 1 /; m==1 || n==0; i[ n_, m_ ] := (i[ n, m ]=1/n Sum[ i[ k, m ] Plus @@ ((# i[ #, m-1 ])& /@ Divisors[ n-k ]), {k, 0, n-1} ]) /; n>0 && m>1
(* Second program: *)
A[0|1, _] = A[_, 1] = 1; A[n_, k_] := A[n, k] = Sum[DivisorSum[j, A[#, k-1] * #&]*A[n-j, k], {j, 1, n}]/n;
a[n_] := A[n, 5];
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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