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 A222180 #65 Mar 09 2018 21:26:25 %S A222180 0,1,6,16,26,36,56,86,106,116,136,176,216,246,296,366,406,416,436,476, %T A222180 536,616 %N A222180 Total number of ON states after n generations of cellular automaton based on pentagons. Also P-toothpick sequence (see Comments lines for definition). %C A222180 Analog of A161644, A147562 and A151723, but here we are working without a lattice. Each regular pentagon has five virtual neighbors. Overlapping are prohibited. The sequence gives the number of pentagons in the structure after n-th stage. A222181 (the first differences) gives the number of pentagons added at n-th stage. %C A222180 Also this is a P-toothpick sequence since every pentagon can be replaced by a P-toothpick which is formed by five toothpicks as a five-pointed star. Note that each toothpick can be represented as an apothem or as a radius of a pentagon. In both types of structures the number of toothpicks after n-th stage is equal to 5*a(n). %H A222180 Omar E. Pol, <a href="http://www.polprimos.com/imagenespub/poltp055.jpg">Illustration of structure after 5 stages</a>, (Contains 36 pentagons). %H A222180 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 A222180 <a href="/index/To#toothpick">Index entries for sequences related to toothpick sequences</a> %F A222180 a(n) = 6 + 10*A222172(n-2), n >= 2. - _Omar E. Pol_, Nov 24 2013 %Y A222180 Cf. A139250, A147562, A151723, A152968, A161330, A161644, A182632, A182840, A222172, A222176, A222181. %K A222180 nonn,more %O A222180 0,3 %A A222180 _Omar E. Pol_, Mar 15 2013 %E A222180 Name improved by _Omar E. Pol_, Nov 24 2013