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 A161910 #10 Jun 14 2022 14:12:05 %S A161910 0,1,2,5,6,9,12,19,22,25,28,35,40,47,56,73 %N A161910 Y-toothpick sequence starting at the corner of an infinite hexagon from which protrudes a half toothpick with an angle = Pi/6. %C A161910 The sequence gives the number of Y-toothpicks in the structure after n rounds. A160123 (the first differences) gives the number added at the n-th round. %C A161910 See the entries A160120, A161830 and A161426 for more information about Y-toothpick sequences. %H A161910 David Applegate, Omar E. Pol and N. J. A. Sloane, <a href="/A000695/a000695_1.pdf">The Toothpick Sequence and Other Sequences from Cellular Automata</a>, Congressus Numerantium, Vol. 206 (2010), 157-191. [There is a typo in Theorem 6: (13) should read u(n) = 4.3^(wt(n-1)-1) for n >= 2.] %H A161910 N. J. A. Sloane, <a href="/wiki/Catalog_of_Toothpick_and_CA_Sequences_in_OEIS">Catalog of Toothpick and Cellular Automata Sequences in the OEIS</a> %F A161910 a(n) = (A160120(n+1)-1)/3. %Y A161910 Cf. A160120, A160121, A160123, A160406, A161426, A161830, A161831. %K A161910 more,nonn %O A161910 0,3 %A A161910 _Omar E. Pol_, Jun 21 2009