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 A211019 #13 Sep 26 2015 01:17:13 %S A211019 0,0,1,2,3,1,10,13,3,1,42,53,13,3,1,170,213,53,13,3,1,682,853,213,53, %T A211019 13,3,1,2730,3413,853,213,53,13,3,1,10922,13653,3413,853,213,53,13,3, %U A211019 1,43690,54613,13653,3413,853,213,53,13,3,1,174762,218453 %N A211019 Triangle read by rows: T(n,k) = number of squares and rectangles of area 2^(k-1) after 2^n stages in the toothpick structure of A139250, divided by 4, n>=1, k>=1, assuming the toothpicks have length 2. %C A211019 All internal regions in the toothpick structure are squares and rectangles. %H A211019 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 A211019 T(n,k) = A211016(n,k)/4. %F A211019 T(n,1) = A020988(n-2), n>=2. %e A211019 Triangle begins: %e A211019 0; %e A211019 0, 1; %e A211019 2, 3, 1; %e A211019 10, 13, 3, 1; %e A211019 42, 53, 13, 3, 1; %e A211019 170, 213, 53, 13, 3, 1; %e A211019 682, 853, 213, 53, 13, 3, 1; %e A211019 2730, 3413, 853, 213, 53, 13, 3, 1; %e A211019 10922, 13653, 3413, 853, 213, 53, 13, 3, 1; %e A211019 43690, 54613, 13653, 3413, 853, 213, 53, 13, 3, 1; %Y A211019 Row sums give 0 together with A014825. %Y A211019 Cf. A002450, A020988, A072197, A086462, A139250, A160124, A211016, A211017, A211018. %K A211019 nonn,tabl %O A211019 1,4 %A A211019 _Omar E. Pol_, Sep 24 2012