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 A169778 #22 Feb 04 2015 23:24:53 %S A169778 0,1,1,1,2,1,2,3,4,1,2,3,5,5,4,7,8,1,2,3,5,5,5,9,13,9,4,7,12,14,10,16, %T A169778 16,1,2,3,5,5,5,9,13,9,5,9,15,19,17,21,29,17,4,7,12,14,14,22,34,30,14, %U A169778 16,28,35,25,35,32,1,2,3,5,5,5,9,13,9,5,9,15,19,17,21 %N A169778 a(n) = ceiling(A170905/2). %C A169778 The hexagon-based CA of A151723 has as symmetry group the dihedral group of order 12. Consider a one-twelfth slice; a(n) is the number of cells that are turned from OFF to ON at generation n. %F A169778 A170905(n) = 2a(n) except A170905(1)=1. %e A169778 Illustration of generations 1 through 9: %e A169778 .1 %e A169778 ..2 %e A169778 ...3 %e A169778 ..4.4 %e A169778 .....5 %e A169778 ..7.6.6 %e A169778 ...7...7 %e A169778 ..8.8.8.8 %e A169778 .........9 %e A169778 ... %e A169778 From _Omar E. Pol_, Feb 12 2013: (Start) %e A169778 When written as a triangle from 1, the right border gives A011782 and row lengths give A011782. %e A169778 1, %e A169778 1, %e A169778 1,2, %e A169778 1,2,3,4, %e A169778 1,2,3,5,5,4,7,8, %e A169778 1,2,3,5,5,5,9,13,9,4,7,12,14,10,16,16, %e A169778 1,2,3,5,5,5,9,13,9,5,9,15,19,17,21,29,17,4,7,12,14,14,22,34,30,14,16,28,35,25,35,32; %e A169778 1,2,3,5,5,5,9,13,9,5,9,15,19,17,21,... (End) %Y A169778 Cf. A151723, A151724, A170905. %K A169778 nonn,tabf %O A169778 0,5 %A A169778 _N. J. A. Sloane_, May 08 2010