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 A220522 #20 Mar 11 2014 01:34:21 %S A220522 0,1,3,7,11,15,19,26,34,38,42,50,62,70,78,91,107,111,115,123,135,151, %T A220522 167,187,211,223,231,247,275,291,307,332,364,368,372,380,392,408,424, %U A220522 446,478,504,524,548,588,620,660,701,749,769,777 %N A220522 Number of toothpicks and D-toothpicks after n-th stage in the D-toothpick "narrow" triangle of the third kind. %C A220522 The structure is essentially one of the oblique wedges of several D-toothpick structures. For more information see A220500. First differs from A194442 at a(47). The first differences (A220523) give the number of toothpicks or D-toothpicks added at n-th stage. %H A220522 Omar E. Pol, <a href="http://www.polprimos.com/imagenespub/poltp064.jpg">Illustration of the structure after 32 stages</a> %H A220522 Omar E. Pol, <a href="http://www.polprimos.com/imagenespub/poltp068.jpg">Illustration of the structure after 64 stages</a> %H A220522 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 A220522 <a href="/index/To#toothpick">Index entries for sequences related to toothpick sequences</a> %Y A220522 Cf. A047999, A139250, A194270, A194700, A194440, A194442, A194444, A220496, A220500, A220523. %K A220522 nonn %O A220522 0,3 %A A220522 _Omar E. Pol_, Dec 15 2012