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 A342434 #19 Dec 15 2022 14:09:53 %S A342434 1,9,17,26,37,47 %N A342434 Solution to stepping stone puzzle on a hexagonal board (See Comments). %C A342434 This is a variant of the stepping stone sequence (A337663), where now the board is a hexagonal grid. %C A342434 Start with an infinite hexagonal grid. Each cell has six neighbors. Place n 1's anywhere. Now place the numbers 2, 3, ..., m in order, subject to the rule that when you place k, the sum of its neighbors must equal k. Then a(n) is the maximum m that can be achieved. %H A342434 Jeremy Rebenstock, <a href="/A342434/a342434.png">Illustration for a(2)</a> %H A342434 Jeremy Rebenstock, <a href="/A342434/a342434_3.png">Illustration for a(5)</a> [Corrected by _Al Zimmermann_, Nov 27 2022] %H A342434 Jeremy Rebenstock, <a href="/A342434/a342434_2.png">Illustration for lower bound</a> %F A342434 a(n) >= 5n - 4. This is seen by constructing the pattern linked above, titled "Illustration for lower bound". %e A342434 Found by code compiled by Hugo van der Sanden and Thomas Ladouceur, see links titled: "Illustration for a(2)" and "Illustration for a(5)". %Y A342434 Cf. A337663. %K A342434 nonn,more,hard %O A342434 1,2 %A A342434 _Jeremy Rebenstock_ and _Thomas Ladouceur_, Mar 12 2021