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 A196052 Sum of the degrees of the nodes at level 1 in the rooted tree with Matula-Goebel number n. 3
 0, 1, 2, 2, 2, 3, 3, 3, 4, 3, 2, 4, 3, 4, 4, 4, 2, 5, 4, 4, 5, 3, 3, 5, 4, 4, 6, 5, 3, 5, 2, 5, 4, 3, 5, 6, 4, 5, 5, 5, 2, 6, 3, 4, 6, 4, 3, 6, 6, 5, 4, 5, 5, 7, 4, 6, 6, 4, 2, 6, 4, 3, 7, 6, 5, 5, 2, 4, 5, 6, 4, 7, 3, 5, 6, 6, 5, 6, 3, 6, 8, 3, 2, 7, 4, 4, 5, 5, 5, 7, 6, 5, 4, 4, 6, 7, 3, 7, 6, 6, 3, 5, 4, 6, 7, 6, 4, 8, 2, 5 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS The Matula-Goebel number of a rooted tree can be 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. REFERENCES 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. LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 E. Deutsch, Tree statistics from Matula numbers, arXiv preprint arXiv:1111.4288, 2011 FORMULA a(1)=0; if n = p(t) (the t-th prime), then a(n)=1+G(t), where G(t) is the number of prime divisors of t counted with multiplicities;  if n=rs (r,s>=2), then a(n)=a(r)+a(s). The Maple program is based on this recursive formula. EXAMPLE a(7)=3 because the rooted tree with Matula-Goebel number 7 is the rooted tree Y. a(2^m) = m because the rooted tree with Matula-Goebel number 2^m is a star with m edges. MAPLE with(numtheory): a := proc (n) local r, s: r := proc (n) options operator, arrow: op(1, factorset(n)) end proc: s := proc (n) options operator, arrow: n/r(n) end proc: if n = 1 then 0 elif bigomega(n) = 1 then 1+bigomega(pi(n)) else a(r(n))+a(s(n)) end if end proc: seq(a(n), n = 1 .. 110); PROG (Haskell) import Data.List (genericIndex) a196052 n = genericIndex a196052_list (n - 1) a196052_list = 0 : g 2 where    g x = y : g (x + 1) where      y = if t > 0 then a001222 t + 1 else a196052 r + a196052 s          where t = a049084 x; r = a020639 x; s = x `div` r -- Reinhard Zumkeller, Sep 03 2013 CROSSREFS Cf. A049084, A020639, A001222. Sequence in context: A131410 A202453 A259529 * A080773 A134598 A325120 Adjacent sequences:  A196049 A196050 A196051 * A196053 A196054 A196055 KEYWORD nonn AUTHOR Emeric Deutsch, Sep 27 2011 STATUS approved

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Last modified May 31 22:45 EDT 2020. Contains 334756 sequences. (Running on oeis4.)