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A004026
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Number of perfect quadratic forms or lattices in dimension n.
(Formerly M0862)
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7
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OFFSET
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1,4
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REFERENCES
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D.-O. Jaquet, Classification des réseaux dans R^7 (via la notion de formes parfaites), Journées Arithmétiques, 1989 (Luminy, 1989). Asterisque No. 198-200 (1991), 7-8, 177-185 (1992).
J. Martinet, Les réseaux parfaits des espaces Euclidiens, Masson, Paris, 1996, p. 175.
J. Martinet, Perfect Lattices in Euclidean Spaces, Springer-Verlag, NY, 2003.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
A. Schürmann, Enumerating perfect forms, Contemporary Math., 493 (2009), 359-377. [From N. J. A. Sloane, Jan 21 2010]
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LINKS
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J. H. Conway and N. J. A. Sloane, Sphere Packings, Lattices and Groups, Springer-Verlag, 3rd edition, 1999, see Preface to 3rd Ed., especially the page that was omitted by the publisher between pages xx and xxi!
A. Schürmann, Enumerating perfect forms, International Conference on the Algebraic and Arithmetic Theory of Quadratic Forms, 2007.
B. Venkov, Réseaux et designs sphériques, pp. 10-86 in Réseaux Euclidiens, Designs Sphériques et Formes Modulaires, ed. J. Martinet, L'Enseignement Mathématique, Geneva, 2001.
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CROSSREFS
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KEYWORD
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hard,more,nonn,nice
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AUTHOR
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EXTENSIONS
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a(8) from the work of Mathieu Dutour Sikiric, Achill Schuermann and Frank Vallentin, Oct 05 2005
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STATUS
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approved
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