1,1

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

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

G. A. Baker et al., On the two-dimensional, spin-1/2 Heisenberg ferromagnetic models, Phys. Lett., 25A (1967), 207-209.

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

Sequence in context: A155130 A083233 A002918 this_sequence A037184 A085457 A105627

Adjacent sequences: A005396 A005397 A005398 this_sequence A005400 A005401 A005402

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