0,2

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

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

G.f.:-2*x*(4*x^2+13*x+4)/(x-1)^5 [From Maksym Voznyy (voznyy(AT)mail.ru), Aug 10 2009]

n*(n+1)*(7*n^2+7*n+2)/4;

Cf. A152041.

Sequence in context: A041114 A015496 A039329 this_sequence A121782 A121781 A121780

Adjacent sequences: A008890 A008891 A008892 this_sequence A008894 A008895 A008896

nonn

N. J. A. Sloane (njas(AT)research.att.com), R. K. Guy