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 A298819 #35 Jan 14 2019 02:58:18 %S A298819 0,0,2,2,2,0,6,6,12,4,28,14,14,0,14,14,84,12,372,62,248,8,504,126,252, %T A298819 28,420,30,30,0,30,30,420,28,2044,1022,12264,24,504,126,7812,124, %U A298819 253828,4094,32752,16,16368,2046,85932,252,18396,1022,4088,56,917448,32766,327660,60,1860,62,62,0,62,62 %N A298819 a(n) is the period of the oscillating pattern formed by a 1 X n line of cells in the Life-like cellular automaton B2c3-cekq4ikt5i8/S2-in3-acky4aijry5eiky6i, or 0 if the pattern vanishes. %C A298819 An explanation of the Hensel notation used to define the cellular automaton rule can be found on the LifeWiki (see links). %H A298819 LifeWiki, <a href="http://www.conwaylife.com/wiki/Isotropic_non-totalistic_Life-like_cellular_automaton">Isotropic non-totalistic Life-like cellular automaton</a> %F A298819 For n divisible by 4, a(n) = A160657(n/4) = (a divisor of) 2^(A003558(n/4) + 1) - 2. %F A298819 With the exception of a(1), all values of n for which a(n) = 0 are of the form 2^m - 2 for some integer m (A000918). %F A298819 a(2k) = A268754(k); a(2k+1) = lcm(A268754(k), A268754(k+1)) (conjectured). Note that, by an arbitrary/cosmetic convention, A268754 uses 1 for empty patterns and A298819 uses 0. - _WG Zeist_ and _Charlie Neder_, Jan 11 2019 %e A298819 a(4) = 2 because a 1 X 4 line oscillates with period 2 in this cellular automaton. %Y A298819 Cf. A000918, A003558, A160657, A268754. %K A298819 nonn %O A298819 1,3 %A A298819 _WG Zeist_, Jan 26 2018