OFFSET
0,1
COMMENTS
The hexagonal lattice is the familiar 2-dimensional lattice in which each point has 6 neighbors. This is sometimes called the triangular lattice.
LINKS
G. Nebe and N. J. A. Sloane, Home page for hexagonal (or triangular) lattice A2
FORMULA
unique(A038587).
MATHEMATICA
CoefficientList[3 QPochhammer[q^3]^3 / QPochhammer[q] + O[q]^100, q] //
Accumulate // DeleteDuplicates (* Jean-François Alcover, Jul 05 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved