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 A136793 Number of unlabeled rooted trees with n 4-colored nodes. 4
 4, 16, 104, 752, 5996, 50512, 444256, 4027360, 37383044, 353486320, 3393093696, 32976302800, 323839605124, 3208549483216, 32033691247528, 321955764477936, 3254812520854980, 33075467402453872, 337670437247448728, 3461635652745799136, 35620112071990294784 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 REFERENCES F. Bergeron, G. Labelle and P. Leroux, Combinatorial Species and Tree-Like Structures, Cambridge, 1998, p. 293 (4.1.60). LINKS L. Foissy, Algebraic structures on typed decorated rooted trees, arXiv:1811.07572 (2018) N. J. A. Sloane, Transforms FORMULA Shifts left and divides by 4 under EULER transform. a(n) = A136794(n)*2 = A052763(n)*4. MAPLE with(numtheory): a:= proc(n) option remember; `if`(n<2, n*4, (add(add(d*       a(d), d=divisors(j))*a(n-j), j=1..n-1))/(n-1))     end: seq(a(n), n=1..25);  # Alois P. Heinz, May 16 2014 MATHEMATICA a[1] = 4; a[n_] := a[n] = Sum[ Sum[ d*a[d], {d, Divisors[j]}]*a[n-j], {j, 1, n-1}]/(n-1); Table[a[n], {n, 1, 25}] (* Jean-François Alcover, Feb 24 2015, after Alois P. Heinz *) CROSSREFS Sequence in context: A094637 A203716 A330537 * A274889 A009630 A318695 Adjacent sequences:  A136790 A136791 A136792 * A136794 A136795 A136796 KEYWORD nonn AUTHOR Christian G. Bower, Jan 21 2008 STATUS approved

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Last modified January 17 20:36 EST 2020. Contains 330987 sequences. (Running on oeis4.)