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%I M1981 #36 Apr 12 2024 11:53:37
%S 0,0,0,0,2,10,110,1722,51039,2560606,215331676,31067572481
%N Number of n-node graphs not determined by their spectrum.
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H Andries E. Brouwer, <a href="http://www.win.tue.nl/~aeb/graphs/cospectral/cospectralA.html">Numbers of characteristic polynomials and cospectral graphs for A</a>
%H A. E. Brouwer and E. Spence, <a href="https://doi.org/10.37236/258">Cospectral graphs on 12 vertices</a>, Electr. J. Combin. 16 (2009) N20. (p. 199).
%H C. Godsil and B. D. McKay, <a href="https://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 Andreas Holmstrom, <a href="https://andreasholmstrom.org/wp-content/2016/05/article-cicm-new-heading-May2016.pdf">A first step towards automated conjecture-making in higher arithmetic geometry</a>, Work-in-progress paper presented at the Conference on Intelligent Computer Mathematics, July 2016. Published in the CEUR Workshop Proceedings.
%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 P. W. Mills, R. P. Rundle, J. H. Samson, Simon J. Devitt, Todd Tilma, V. M. Dwyer, and Mark J. Everitt, <a href="https://doi.org/10.1103/PhysRevA.100.052317">Quantum invariants and the graph isomorphism problem</a>, Phys. Rev. A 100, 052317 (2019).
%H E. Spence, <a href="http://www.maths.gla.ac.uk/~es/cospec/cospec.php">Numbers of characteristic polynomials and cospectral graphs for A</a>
%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/CospectralGraphs.html">Cospectral Graphs</a>
%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/DeterminedbySpectrum.html">Determined by Spectrum</a>
%Y Cf. A178925 (simple graphs determined by spectrum), A099881, A099882.
%K nonn,hard,more,changed
%O 1,5
%A _N. J. A. Sloane_
%E a(10) from _Eric W. Weisstein_, Dec 30 2010
%E Two more terms from _Ruperto Corso_, Dec 18 2011
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