A253079 a(n) = if n is even, number of ON cells at stage n of two-dimensional 5-neighbor outer totalistic cellular automaton defined by "Rule 489" or if n is odd, number of OFF cells.

1, 5, 13, 17, 33, 21, 65, 65, 97, 61, 145, 153, 177, 149, 257, 249, 345, 237, 433, 409, 465, 389, 601, 521, 745, 501, 897, 713, 897, 709, 1081, 921, 1281, 877, 1481, 1121, 1505, 1125, 1817, 1393, 1993, 1309, 2209, 1577, 2401, 1653, 2497, 1953, 2985, 1901

Offset: 0

Author

N. J. A. Sloane, Feb 04 2015

Keywords

• nonn

Comments

If we subtract 1 and divide by 4, the result (A253080) almost looks like it should have a simple recurrence. It would be nice to know more.

References

• S. Wolfram, A New Kind of Science, Wolfram Media, 2002; pp. 173-175.

Links

• N. J. A. Sloane, Illustration of generations 0-23
• Index entries for sequences related to cellular automata

Crossrefs

Cf. A253080, A169699, A246316, A246318, A246325, A246326, ...

Programs

Mathematica

Map[Function[Apply[Plus, Flatten[ #1]]], CellularAutomaton[{ 489, {2, {{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}}, {1, 1}}, {{{1}}, 0}, 200]] (* then subtract the odd-indexed terms from 201^2 (a constant which depends on Mathematica's choice of grid size) *)
ArrayPlot /@ CellularAutomaton[{489, {2, {{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}}, {1, 1}}, {{{1}}, 0}, 23]