0

Row n has length 2n+1.

This sequence is also generated by Rule 43.

S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 55.

Robert Price, Table of n, a(n) for n = 0..9999

Eric Weisstein's World of Mathematics, Elementary Cellular Automaton

S. Wolfram, A New Kind of Science

The first ten rows:

1

1 0 0

0 0 0 1 1

1 1 1 1 1 0 0

0 0 0 0 0 0 0 1 1

1 1 1 1 1 1 1 1 1 0 0

0 0 0 0 0 0 0 0 0 0 0 1 1

1 1 1 1 1 1 1 1 1 1 1 1 1 0 0

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0

The full array including leading and trailing 0's and 1's has this shape:

00000000000000100000000000000

11111111111111001111111111111

00000000000000011000000000000

11111111111111110011111111111

00000000000000000110000000000

11111111111111111100111111111

00000000000000000001100000000

11111111111111111111001111111

00000000000000000000011000000

11111111111111111111110011111

00000000000000000000000110000

11111111111111111111111100111

00000000000000000000000001100

11111111111111111111111111001

- R. J. Mathar, Aug 08 2025

rule=11; 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 *) Flatten[catri] (* Triangle Representation of CA *)

Sequence in context: A015780 A011642 A016338 * A113052 A369967 A256432

Adjacent sequences: A266250 A266251 A266252 * A266254 A266255 A266256

nonn,tabf,easy

Robert Price, Dec 25 2015

approved