This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A038588 #11 Jul 08 2025 22:24:55 %S A038588 3,6,12,18,21,27,30,36,42,48,54,63,69,75,78,84,90,96,102,114,120,123, %T A038588 129,135,141,144,150,156,168,174,180,186,192,198,207,213,219,225,231, %U A038588 240,246,252,258,270,276,282 %N A038588 Sizes of clusters in hexagonal lattice A_2 centered at deep hole. %C A038588 The hexagonal lattice is the familiar 2-dimensional lattice in which each point has 6 neighbors. This is sometimes called the triangular lattice. %H A038588 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> %F A038588 unique(A038587). %t A038588 CoefficientList[3 QPochhammer[q^3]^3 / QPochhammer[q] + O[q]^100, q] // %t A038588 Accumulate // DeleteDuplicates (* _Jean-François Alcover_, Jul 05 2019 *) %Y A038588 Cf. A005882, A038587. %K A038588 nonn %O A038588 0,1 %A A038588 _N. J. A. Sloane_