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 A038587 #13 Jul 08 2025 22:24:48 %S A038587 3,6,12,12,18,21,27,27,30,36,42,42,48,48,54,54,63,69,69,69,75,78,84, %T A038587 84,90,96,102,102,102,102,114,114,120,123,129,129,135,141,141,141,144, %U A038587 150,156,156,168,168,174,174,174 %N A038587 Sizes of successive clusters in hexagonal lattice A_2 centered at deep hole. %C A038587 The hexagonal lattice is the familiar 2-dimensional lattice in which each point has 6 neighbors. This is sometimes called the triangular lattice. %H A038587 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 A038587 CoefficientList[3 QPochhammer[q^3]^3 / QPochhammer[q] + O[q]^50, q] // Accumulate (* _Jean-François Alcover_, Jul 05 2019 *) %Y A038587 Partial sums of A005882. %Y A038587 Cf. A038588. %K A038587 nonn %O A038587 0,1 %A A038587 _N. J. A. Sloane_