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 A171176 #16 Jun 26 2022 12:19:34
%S A171176 2,1,5,3,2,1,8,5,4,3,2,1,11,7,6,5,4,3,2,1,14,9,8,7,6,5,4,3,2,1,17,11,
%T A171176 10,9,8,7,6,5,4,3,2,1,20,13,12,11,10,9,8,7,6,5,4,3,2,1,23,15,14,13,12,
%U A171176 11,10,9,8,7,6,5,4,3,2,1,26,17,16,15,14,13,12,11,10,9,8,7,6,5,4,3,2,1
%N A171176 Triangle read by rows in which row n lists 3n-1 together with the first 2n-1 positive integers, in reverse order.
%C A171176 a(n) is also the length of the n-th L-toothpick added to the structure of A171166.
%H A171176 Harvey P. Dale, <a href="/A171176/b171176.txt">Table of n, a(n) for n = 1..1000</a>
%H A171176 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>
%H A171176 <a href="/index/To#toothpick">Index entries for sequences related to toothpick sequences</a>
%e A171176 Triangle begins:
%e A171176 2, 1;
%e A171176 5, 3, 2, 1;
%e A171176 8, 5, 4, 3, 2, 1;
%e A171176 11, 7, 6, 5, 4, 3, 2, 1;
%e A171176 14, 9, 8, 7, 6, 5, 4, 3, 2, 1;
%e A171176 17, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1;
%e A171176 20, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1;
%e A171176 23, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1;
%e A171176 26, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1;
%t A171176 Table[{3n-1,Reverse[Range[2n-1]]},{n,10}]//Flatten (* _Harvey P. Dale_, Jun 26 2022 *)
%Y A171176 Cf. A000027, A016789, A172310, A171164, A161165, A161166, A171172, A171173, A171174, A171175, A171177, A171178.
%Y A171176 Cf. A132209 (row sums). - _R. J. Mathar_, Mar 01 2010
%K A171176 easy,nonn,tabf
%O A171176 1,1
%A A171176 _Omar E. Pol_, Feb 23 2010