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Number of n-node trees not determined by their spectra.
(Formerly M1959)
0

%I M1959 #22 Mar 31 2022 21:59:18

%S 0,0,0,0,0,0,0,2,10,8,60,119,415,826,2470,5246,14944,32347,84118

%N Number of n-node trees not determined by their spectra.

%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

%H C. Godsil and B. D. McKay, <a href="http://doi.org/10.1007/BFb0097370">Some computational results on the spectra of graphs</a>, pp. 73-92 of Combinatorial Mathematics IV (Adelaide 1975), Lect. Notes Math., 560 (1976).

%H Jürgen Jost, Raffaella Mulas, and Leo Torres, <a href="https://arxiv.org/abs/2203.10824">Spectral theory of the non-backtracking Laplacian for graphs</a>, arXiv:2203.10824 [math.SP], 2022.

%H <a href="/index/Tra#trees">Index entries for sequences related to trees</a>

%K nonn,more

%O 1,8

%A _N. J. A. Sloane_.

%E Existing terms verified and a(19) from _Sean A. Irvine_, May 14 2017