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A052854 Number of forests of ordered trees on n total nodes. 5
1, 1, 2, 4, 10, 26, 77, 235, 758, 2504, 8483, 29203, 102030, 360442, 1285926, 4625102, 16754302, 61067430, 223803775, 824188993, 3048383517, 11318928477, 42176798315, 157664823501, 591109863049, 2222121888117, 8374151243258, 31630394287364, 119725350703472 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

If B is a collection in which there are A000108(n-1) [Catalan numbers] things with n points, a(n) is the number of multisets of B with a total of n points.

REFERENCES

Florian Luca, Pantelimon Stanica, On the Euler function of the Catalan numbers, Journal of Number Theory, Volume 132, Issue 7, July 2012, Pages 1404-1424.

LINKS

T. D. Noe and Alois P. Heinz, Table of n, a(n) for n = 0..1000 (first 201 terms from T. D. Noe)

Steven R. Finch, Errata and Addenda to Mathematical Constants, p. 40.

Steven R. Finch, Errata and Addenda to Mathematical Constants, January 22, 2016. [Cached copy, with permission of the author]

P. Flajolet et al., A hybrid of Darboux's method and singularity analysis in combinatorial asymptotics, arXiv:math/0606370 [math.CO], 2006.

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 822

FORMULA

Euler transform of Catalan numbers C(n-1) (cf. A000108).

n*a(n)=Sum_{k=1..n} a(n-k)*b(k), b(k)=Sum_{d|k} binomial(2*d-2, d-1)=A066768(k). - Vladeta Jovovic, Jan 17 2002

G.f.: 1/(Product_{k>0} (1-x^k)^C(k-1)) where C() is Catalan numbers.

G.f.: A(z) = prod_{n >= 1} (1-z^n)^(-A000108(n)) = exp(sum_{k >= 1} C(z^k)/k, where C(z) is the g.f. for the Catalan numbers.

a(n) ~ K 4^(n-1)/sqrt(Pi n^3), where K ~ 1.71603053492228196404746... (see A246949).

MAPLE

spec := [S, {B=Sequence(C), C=Prod(Z, B), S=Set(C)}, unlabeled]: seq(combstruct[count](spec, size=n), n=0..20); # version 1

spec := [ C, {B=Union(Z, Prod(B, B)), C=Set(B)}, unlabeled ]; [seq(combstruct[count](spec, size=n), n=0..40)]; # version 2

# third Maple program:

with(numtheory):

b:= proc(n) option remember; binomial(2*n, n) end:

a:= proc(n) option remember; `if`(n=0, 1, add(add(

      b(d-1), d=divisors(j))*a(n-j), j=1..n)/n)

    end:

seq(a(n), n=0..35);  # Alois P. Heinz, Mar 10 2015

MATHEMATICA

max = 27; f[x_] := 1/Product[ (1 - x^k)^CatalanNumber[k - 1], {k, 1, max}]; se = Series[f[x], {x, 0, max}]; CoefficientList[se, x] (* Jean-Fran├žois Alcover, Oct 05 2011, after g.f. *)

PROG

(PARI) a(n)=if(n<0, 0, polcoeff(1/prod(k=1, n, (1-x^k+x*O(x^n))^((2*k-2)!/k!/(k-1)!)), n))

CROSSREFS

Cf. A000108, A052805, A066768.

Cf. A246949.

Sequence in context: A149817 A149818 A148101 * A148102 A179381 A096807

Adjacent sequences:  A052851 A052852 A052853 * A052855 A052856 A052857

KEYWORD

easy,nonn,nice

AUTHOR

encyclopedia(AT)pommard.inria.fr, Jan 25 2000

EXTENSIONS

Better title from Geoffrey Critzer, Feb 22 2013

Minor edits, Vaclav Kotesovec, May 13 2014

STATUS

approved

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Last modified October 22 16:20 EDT 2019. Contains 328318 sequences. (Running on oeis4.)