cp's OEIS Frontend

A253066 Number of odd terms in f^n, where f = 1/x+1+x+1/y+y/x+x*y.

%I A253066 #24 Jul 12 2017 03:20:18
%S A253066 1,6,6,28,6,36,28,112,6,36,36,168,28,168,112,456,6,36,36,168,36,216,
%T A253066 168,672,28,168,168,784,112,672,456,1816,6,36,36,168,36,216,168,672,
%U A253066 36,216,216,1008,168,1008,672,2736,28,168,168,784,168,1008,784,3136,112,672,672,3136,456,2736,1816,7288
%N A253066 Number of odd terms in f^n, where f = 1/x+1+x+1/y+y/x+x*y.
%C A253066 This is the number of ON cells in a certain 2-D CA in which the neighborhood of a cell is defined by f, and in which a cell is ON iff there was an odd number of ON cells in the neighborhood at the previous generation.
%C A253066 This is the odd-rule cellular automaton defined by OddRule 275 (see Ekhad-Sloane-Zeilberger "Odd-Rule Cellular Automata on the Square Grid" link).
%H A253066 Alois P. Heinz, <a href="/A253066/b253066.txt">Table of n, a(n) for n = 0..8191</a>
%H A253066 Shalosh B. Ekhad, N. J. A. Sloane, and  Doron Zeilberger, <a href="http://arxiv.org/abs/1503.01796">A Meta-Algorithm for Creating Fast Algorithms for Counting ON Cells in Odd-Rule Cellular Automata</a>, arXiv:1503.01796 [math.CO], 2015; see also the <a href="http://www.math.rutgers.edu/~zeilberg/mamarim/mamarimhtml/CAcount.html">Accompanying Maple Package</a>.
%H A253066 Shalosh B. Ekhad, N. J. A. Sloane, and  Doron Zeilberger, <a href="http://arxiv.org/abs/1503.04249">Odd-Rule Cellular Automata on the Square Grid</a>, arXiv:1503.04249 [math.CO], 2015.
%H A253066 N. J. A. Sloane, On the No. of ON Cells in Cellular Automata, Video of talk in Doron Zeilberger's Experimental Math Seminar at Rutgers University, Feb. 05 2015: <a href="https://vimeo.com/119073818">Part 1</a>, <a href="https://vimeo.com/119073819">Part 2</a>
%H A253066 N. J. A. Sloane, <a href="http://arxiv.org/abs/1503.01168">On the Number of ON Cells in Cellular Automata</a>, arXiv:1503.01168 [math.CO], 2015.
%H A253066 <a href="/index/Ce#cell">Index entries for sequences related to cellular automata</a>
%F A253066 This is the Run Length Transform of A253068.
%e A253066 Here is the neighborhood f:
%e A253066 [X, 0, X]
%e A253066 [X, X, X]
%e A253066 [0, X, 0]
%e A253066 which contains a(1) = 6 ON cells.
%p A253066 C:=f->subs({x=1, y=1}, f);
%p A253066 # Find number of ON cells in CA for generations 0 thru M defined by rule
%p A253066 # that cell is ON iff number of ON cells in nbd at time n-1 was odd
%p A253066 # where nbd is defined by a polynomial or Laurent series f(x, y).
%p A253066 OddCA:=proc(f, M) global C; local n, a, i, f2, p;
%p A253066 f2:=simplify(expand(f)) mod 2;
%p A253066 a:=[]; p:=1;
%p A253066 for n from 0 to M do a:=[op(a), C(p)]; p:=expand(p*f2) mod 2; od:
%p A253066 lprint([seq(a[i], i=1..nops(a))]);
%p A253066 end;
%p A253066 f:=1/x+1+x+1/y+y/x+x*y;
%p A253066 OddCA(f, 130);
%t A253066 (* f = A253068 *) f[0] = 1; f[n_] := ((-2)^n + 4^(n+2)-8)/9; Table[Times @@ (f[Length[#]]&) /@ Select[s = Split[IntegerDigits[n, 2]], #[[1]] == 1 &], {n, 0, 63}] (* _Jean-François Alcover_, Jul 12 2017 *)
%Y A253066 Other CA's that use the same rule but with different cell neighborhoods: A160239, A102376, A071053, A072272, A001316, A246034, A246035, A253064, A253065.
%Y A253066 Cf. A253068.
%K A253066 nonn
%O A253066 0,2
%A A253066 _N. J. A. Sloane_, Jan 29 2015