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 A198340 The overall Wiener index of the rooted tree having Matula-Goebel number n. 1
 0, 1, 6, 6, 21, 21, 24, 24, 56, 56, 56, 67, 67, 67, 126, 80, 67, 161, 80, 154, 154, 126, 161, 197, 252, 161, 354, 188, 154, 333, 126, 240, 252, 154, 311, 440, 197, 197, 333, 414, 161, 411, 188, 311, 683, 354, 333, 545, 384, 636, 311, 411, 240, 921, 462, 510 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS The overall Wiener index of any connected graph G is defined as the sum of the Wiener indices of all the subgraphs of G. The Wiener index of a connected graph is the sum of the distances between all unordered pairs of vertices in the graph. 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. D. Bonchev, The overall Wiener index - a new tool for characterization of molecular topology, J. Chem. Inf. Comput. Sci., 2001, 41, 582-592. LINKS E. Deutsch, Rooted tree statistics from Matula numbers, arXiv:1111.4288. FORMULA A198339(n) gives the sequence of the Matula-Goebel numbers of all the subtrees of the rooted tree with Matula-Goebel number n. A196051(k) is the Wiener number of the rooted tree with Matula-Goebel number k. EXAMPLE a(4)=6 because the rooted tree with Matula-Goebel number 4 is V; each of the 3 one-vertex subtrees has Wiener index 0, each of the 2 one-edge subtrees has Wiener index 1, and the tree V itself has Wiener index 4; 0+0+0+1+1+4=6. MAPLE m2union := proc (x, y) sort([op(x), op(y)]) end proc: with(numtheory); MRST := 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 [1] elif bigomega(n) = 1 then [1, seq(ithprime(mrst[pi(n)][i]), i = 1 .. nops(mrst[pi(n)]))] else [seq(seq(mrst[r(n)][i]*mrst[s(n)][j], i = 1 .. nops(mrst[r(n)])), j = 1 .. nops(mrst[s(n)]))] end if end proc: MNRST := 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 [] elif bigomega(n) = 1 then m2union(mrst[pi(n)], mnrst[pi(n)]) else m2union(mnrst[r(n)], mnrst[s(n)]) end if end proc: MST := proc (n) m2union(mrst[n], mnrst[n]) end proc: for n to 2000 do mrst[n] := MRST(n): mnrst[n] := MNRST(n): mst[n] := MST(n) end do: W := proc (n) local u, v, E, PL: u := proc (n) options operator, arrow: op(1, factorset(n)) end proc: v := proc (n) options operator, arrow: n/u(n) end proc: E := proc (n) if n = 1 then 0 elif bigomega(n) = 1 then 1+E(pi(n)) else E(u(n))+E(v(n)) end if end proc: PL := proc (n) if n = 1 then 0 elif bigomega(n) = 1 then 1+E(pi(n))+PL(pi(n)) else PL(u(n))+PL(v(n)) end if end proc: if n = 1 then 0 elif bigomega(n) = 1 then W(pi(n))+PL(pi(n))+1+E(pi(n)) else W(u(n))+W(v(n))+PL(u(n))*E(v(n))+PL(v(n))*E(u(n)) end if end proc: OW := proc (n) options operator, arrow: add(W(MST(n)[j]), j = 1 .. nops(MST(n))) end proc: seq(OW(n), n = 1 .. 60); CROSSREFS Cf. A196051, A198339. Sequence in context: A004983 A298936 A034695 * A189980 A188273 A185786 Adjacent sequences:  A198337 A198338 A198339 * A198341 A198342 A198343 KEYWORD nonn AUTHOR Emeric Deutsch, Dec 04 2011 STATUS approved

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Last modified January 20 21:36 EST 2019. Contains 319336 sequences. (Running on oeis4.)