%I #11 Jul 05 2019 03:10:57
%S 3,6,12,12,18,21,27,27,30,36,42,42,48,48,54,54,63,69,69,69,75,78,84,
%T 84,90,96,102,102,102,102,114,114,120,123,129,129,135,141,141,141,144,
%U 150,156,156,168,168,174,174,174
%N Sizes of successive clusters in hexagonal lattice A_2 centered at deep hole.
%C The hexagonal lattice is the familiar 2-dimensional lattice in which each point has 6 neighbors. This is sometimes called the triangular lattice.
%H G. Nebe and N. J. A. Sloane, <a href="http://www.math.rwth-aachen.de/~Gabriele.Nebe/LATTICES/A2.html">Home page for hexagonal (or triangular) lattice A2</a>
%t CoefficientList[3 QPochhammer[q^3]^3 / QPochhammer[q] + O[q]^50, q] // Accumulate (* _Jean-François Alcover_, Jul 05 2019 *)
%Y Partial sums of A005882.
%Y Cf. A038588.
%K nonn
%O 0,1
%A _N. J. A. Sloane_.