0,3

J. H. Conway and N. J. A. Sloane, "Sphere Packings, Lattices and Groups", Springer-Verlag, p. 15.

A001116 / 2.

Sequence in context: A079983 A028926 A038577 this_sequence A028924 A034738 A054064

Adjacent sequences: A028922 A028923 A028924 this_sequence A028926 A028927 A028928

nonn,hard

N. J. A. Sloane (njas(AT)research.att.com).