OFFSET
0,2
REFERENCES
S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 55.
LINKS
Robert Price, Table of n, a(n) for n = 0..500
Eric Weisstein's World of Mathematics, Elementary Cellular Automaton
FORMULA
Empirical g.f.: (1 + 3*x - 2*x^2 + x^3 + x^4)/(-1 + x^2)^2. - Michael De Vlieger, Dec 29 2015
Conjectures from Colin Barker, Dec 30 2015 and Apr 15 2019: (Start)
a(n) = (1-(-1)^n)*(2*n+1)/2 for n>0.
a(n) = 2*a(n-2)-a(n-4) for n>4.
(End)
a(n) = A266220(n), n>1. - R. J. Mathar, Jan 10 2016
MATHEMATICA
rule=23; rows=20; ca=CellularAutomaton[rule, {{1}, 0}, rows-1, {All, All}]; (* Start with single black cell *) catri=Table[Take[ca[[k]], {rows-k+1, rows+k-1}], {k, 1, rows}]; (* Truncated list of each row *) Table[Total[catri[[k]]], {k, 1, rows}] (* Number of Black cells in stage n *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Robert Price, Dec 29 2015
STATUS
approved