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 A006984 Greatest minimal norm of sublattice of index n in hexagonal lattice. (Formerly M2298) 3
 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 (list; graph; refs; listen; history; text; internal format)
 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 * A087275 A265305 A072942 Adjacent sequences: A006981 A006982 A006983 * A006985 A006986 A006987 KEYWORD nonn,nice AUTHOR STATUS approved

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Last modified January 27 01:46 EST 2023. Contains 359836 sequences. (Running on oeis4.)