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 A261834 #37 Apr 22 2024 21:44:52 %S A261834 1,6,48,468,5328,68928,994464,15781920,272594160,5081825664 %N A261834 Number of n-step adjacent expansions on the hexagonal (honeycomb) lattice. Holes allowed. %C A261834 Initially only one cell C[0] is occupied on the lattice. %C A261834 Then, for each i of (1..n), C[i] is chosen among the free cells adjacent to at least one of (C[0],...,C[i-1]). %C A261834 a(n) is the number of distinct (C[1],...,C[n]). %H A261834 Francois Alcover, <a href="/A261834/a261834.png">tree</a>. %e A261834 a(1) = 6 because a point has 6 neighbors on the hexagonal grid. %e A261834 a(2) = 48 = a(1) * 8 because a two-cell group has 8 free neighbors. %Y A261834 Cf. A007846 (same principle but on the rectangular lattice). %Y A261834 Cf. A001334. %K A261834 nonn,more %O A261834 0,2 %A A261834 _Francois Alcover_, Mar 24 2016 %E A261834 More terms from _Francois Alcover_, Apr 29 2016 %E A261834 Rephrasing and culling comments from _Francois Alcover_, Apr 29 2016 %E A261834 Added crossref to A007846 from _Francois Alcover_, May 01 2016