A006984 Greatest minimal norm of sublattice of index n in hexagonal lattice. (Formerly M2298)

1, 1, 3, 4, 3, 4, 7, 7, 9, 7, 7, 12, 13, 12, 13, 16, 13, 13, 19, 16, 21, 19, 19, 21, 25, 21, 27, 28, 21, 27, 31, 28, 27, 28, 31, 36, 37, 31, 39, 37, 37, 36, 43, 39, 39, 39, 39, 48, 49, 43, 43

Offset

1,3

Comments

The hexagonal lattice is the familiar 2-dimensional lattice in which each point has 6 neighbors. This is sometimes called the triangular lattice.

References

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

Links

Andrey Zabolotskiy, Table of n, a(n) for n = 1..500

M. Bernstein, N. J. A. Sloane and P. E. Wright, On Sublattices of the Hexagonal Lattice, Discrete Math. 170 (1997) 29-39 (Abstract, pdf, ps).

G. Nebe and N. J. A. Sloane, Home page for hexagonal (or triangular) lattice A2.

N. J. A. Sloane, Computer printout with notes, Mar. 1994.

Crossrefs

Cf. A003051, A003050, A001615.

Sequence in context: A094151 A135800 A178152 * A361458 A087275 A265305

Adjacent sequences: A006981 A006982 A006983 * A006985 A006986 A006987

Keyword

nonn,nice

Author

N. J. A. Sloane, Mira Bernstein

Status

approved