

A212631


Number of dominating subsets of the rooted tree with MatulaGoebel number n.


13



1, 3, 5, 5, 9, 9, 9, 9, 17, 17, 17, 15, 15, 15, 31, 17, 15, 27, 17, 29, 29, 31, 27, 27, 57, 27, 53, 25, 29, 51, 31, 33, 57, 29, 53, 45, 27, 27, 51, 53, 27, 45, 25, 53, 97, 53, 51, 51, 49, 97, 53, 45, 33, 81, 105, 45, 53, 51, 29, 87, 45, 57, 89, 65, 93, 93, 27
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OFFSET

1,2


COMMENTS

The MatulaGoebel number of a rooted tree can be defined in the following recursive manner: to the onevertex tree there corresponds the number 1; to a tree T with root degree 1 there corresponds the tth prime number, where t is the MatulaGoebel number of the tree obtained from T by deleting the edge emanating from the root; to a tree T with root degree m>=2 there corresponds the product of the MatulaGoebel numbers of the m branches of T.
a(n) = Sum(A212630(n,k), k>=1).
a(n) is odd (see the BrouwerCsorbaSchrijver reference).


REFERENCES

A. E. Brouwer, P. Csorba, and A. Schrijver, The number of dominating sets of a finite graph is odd. Preprint available on A. E. Brouwer's homepage.
É. Czabarka, L. Székely, and S. Wagner, The inverse problem for certain tree parameters, Discrete Appl. Math., 157, 2009, 33143319.
F. Goebel, On a 11 correspondence between rooted trees and natural numbers, J. Combin. Theory, B 29 (1980), 141143.
I. Gutman and A. Ivic, On Matula numbers, Discrete Math., 150, 1996, 131142.
I. Gutman and YN. Yeh, Deducing properties of trees from their Matula numbers, Publ. Inst. Math., 53 (67), 1993, 1722.
D. W. Matula, A natural rooted tree enumeration by prime factorization, SIAM Review, 10, 1968, 273.


LINKS

Table of n, a(n) for n=1..67.
S. Alikhani and Y. H. Peng, Introduction to domination polynomial of a graph, arXiv:0905.2251.
E. Deutsch, Rooted tree statistics from Matula numbers, arXiv:1111.4288.
Index entries for sequences related to MatulaGoebel numbers


FORMULA

In A212630 one gives the domination polynomial P(n)=P(n,x) of the rooted tree with MatulaGoebel number n. We have a(n) = P(n,1).


EXAMPLE

a(3)=5 because the rooted tree with MatulaGoebel number 3 is the path tree R  A  B; its dominating subsets are {A}, {R,A}, {R,B}, {A,B}, and {R,A,B}.


MAPLE

with(numtheory): P := proc (n) local r, s, A, B, C: r := n> op(1, factorset(n)): s := n> n/r(n): A := proc (n) if n = 1 then x elif bigomega(n) = 1 then x*(A(pi(n))+B(pi(n))+C(pi(n))) else A(r(n))*A(s(n))/x end if end proc: B := proc (n) if n = 1 then 0 elif bigomega(n) = 1 then A(pi(n)) else sort(expand(B(r(n))*B(s(n))+B(r(n))*C(s(n))+B(s(n))*C(r(n)))) end if end proc: C := proc (n) if n = 1 then 1 elif bigomega(n) = 1 then B(pi(n)) else expand(C(r(n))*C(s(n))) end if end proc: sort(expand(A(n)+B(n))) end proc: seq(subs(x = 1, P(n)), n = 1 .. 100);


CROSSREFS

Cf. A212618  A212632.
Sequence in context: A229428 A029639 A087349 * A090792 A076877 A120841
Adjacent sequences: A212628 A212629 A212630 * A212632 A212633 A212634


KEYWORD

nonn


AUTHOR

Emeric Deutsch, Jun 11 2012


STATUS

approved



