In mathematics, II25,1 is the even 26-dimensional Lorentzian unimodular lattice. It has several unusual properties, arising from Conway's discovery that it has a norm zero Weyl vector. In particular it is closely related to the Leech lattice, and has the Conway group Co1 at the top of its automorphism group.
P. Eklund, J. Ducrou, и T. Wilson. Proceedings of the 4th International Confernce on Concept Lattices and Their Applications, Springer-Verlag, (октября 2006)