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A184159
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The difference between the levels of the highest and lowest leaves in the rooted tree with Matula-Goebel number n.
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0
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0, 0, 0, 0, 0, 1, 0, 0, 0, 2, 0, 1, 1, 1, 1, 0, 0, 1, 0, 2, 0, 3, 0, 1, 0, 2, 0, 1, 2, 2, 0, 0, 2, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 3, 1, 2, 1, 1, 0, 2, 1, 2, 0, 1, 1, 1, 0, 3, 0, 2, 1, 4, 0, 0, 1, 3, 0, 2, 1, 2, 2, 1, 0, 2, 1, 1, 2, 2, 3, 2, 0, 3, 0, 1, 0, 2, 2, 3, 1, 2, 1, 2, 3, 3, 1, 1, 0, 1, 2, 2, 2, 2, 0, 2, 1, 1, 1, 1, 2, 3
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OFFSET
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1,10
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COMMENTS
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The Matula-Goebel number of a rooted tree is defined in the following recursive manner: to the one-vertex tree there corresponds the number 1; to a tree T with root degree 1 there corresponds the t-th prime number, where t is the Matula-Goebel 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 Matula-Goebel numbers of the m branches of T.
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REFERENCES
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F. Goebel, On a 1-1-correspondence between rooted trees and natural numbers, J. Combin. Theory, B 29 (1980), 141-143.
I. Gutman and A. Ivic, On Matula numbers, Discrete Math., 150, 1996, 131-142.
I. Gutman and Yeong-Nan Yeh, Deducing properties of trees from their Matula numbers, Publ. Inst. Math., 53 (67), 1993, 17-22.
D. W. Matula, A natural rooted tree enumeration by prime factorization, SIAM Review, 10, 1968, 273.
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LINKS
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FORMULA
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In A184154 one constructs for each n the generating polynomial P(n,x) of the leaves of the rooted tree with Matula-Goebel number n, according to their levels. a(n) = degree of the numerator of P(n,1/x) (see the Maple program).
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EXAMPLE
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a(7)=0 because the rooted tree with Matula-Goebel number 7 is the rooted tree Y with all leaves at level 2.
a(2^m)=0 because the rooted tree with Matula-Goebel number 2^m is the star with m edges; all leaves are at level 1.
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MAPLE
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with(numtheory): a := proc (n) local r, s, P: r := proc (n) options operator, arrow: op(1, factorset(n)) end proc: s := proc (n) options operator, arrow: n/r(n) end proc: P := proc (n) if n = 1 then 1 elif bigomega(n) = 1 then sort(expand(x*P(pi(n)))) else sort(P(r(n))+P(s(n))) end if end proc: degree(numer(subs(x = 1/x, P(n)))) end proc; seq(a(n), n = 1 .. 110);
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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