%I
%S 0,0,0,0,0,0,0,0,1,1,1,0,7,8,22,25,66,73,204,231,513,576,1520,1715,
%T 3763,4085
%N Number of trees T of order n such that W(T) = W(L(L(T)) where W(G) and L(G) are the Wiener index and line graph of a graph G.
%D A. A. Dobrynin (dobr(AT)math.nsc.ru), Distance of iterated line graphs, Graph Theory Notes of NY, 37 (1999), 89.
%D A. A. Dobrynin and L. S. Mel'nikov, Some results on the Wiener index of iterated line graphs, Electronic Notes in Discrete Mathematics 22 (2005), 469475
%H <a href="/index/Tra#trees">Index entries for sequences related to trees</a>
%o (Sage) # needs the package nauty
%o def a(n):
%o c = 0
%o for el in graphs.nauty_geng(str(n) + ' c ' + str(n1)+':' + str(n1)):
%o g = (el.line_graph()).line_graph()
%o if el.wiener_index() == g.wiener_index():
%o c+=1
%o return c
%o # _Jernej Azarija_, Aug 13 2012
%K nonn
%O 1,13
%A _N. J. A. Sloane_
%E More terms (from Dobrynin/Mel'nikov reference), _Jernej Azarija_, Aug 13 2012
