

A147562


Number of "ON" cells at nth stage in the "UlamWarburton" twodimensional cellular automaton.


85



0, 1, 5, 9, 21, 25, 37, 49, 85, 89, 101, 113, 149, 161, 197, 233, 341, 345, 357, 369, 405, 417, 453, 489, 597, 609, 645, 681, 789, 825, 933, 1041, 1365, 1369, 1381, 1393, 1429, 1441, 1477, 1513, 1621, 1633, 1669, 1705, 1813, 1849, 1957, 2065, 2389, 2401, 2437, 2473
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OFFSET

0,3


COMMENTS

Studied by Holladay and Ulam circa 1960. See Fig. 1 and Example 1 of the Ulam reference.  N. J. A. Sloane, Aug 02 2009.
Singmaster calls this the UlamWarburton cellular automaton.  N. J. A. Sloane, Aug 05 2009
On the infinite square grid, start with all cells OFF.
Turn a single cell to the ON state.
At each subsequent step, each cell with exactly one neighbor ON is turned ON, and everything that is already ON remains ON.
Here "neighbor" refers to the four adjacent cells in the X and Y directions.
Note that "neighbor" could equally well refer to the four adjacent cells in the diagonal directions, since the graph formed by Z^2 with "onestep rook" adjacencies is isomorphic to Z^2 with "onestep bishop" adjacencies.
Also toothpick sequence starting with a central Xtoothpick followed by Ttoothpicks (see A160170 and A160172). The sequence gives the number of polytoothpicks in the structure after nth stage.  Omar E. Pol, Mar 28 2011
It appears that this sequence shares infinitely many terms with both A162795 and A169707, see Formula section and Example section.  Omar E. Pol, Feb 20 2015
It appears that the positive terms are also the odd terms (a bisection) of A151920.  Omar E. Pol, Mar 06 2015
Also, the number of active (ON,black) cells in the nth stage of growth of twodimensional cellular automaton defined by Wolfram's "Rule 558" or "Rule 686" based on the 5celled von Neumann neighborhood.  Robert Price, May 10 2016


REFERENCES

D. Singmaster, On the cellular automaton of Ulam and Warburton, M500 Magazine of the Open University, #195 (December 2003), pp. 27.
S. Ulam, On some mathematical problems connected with patterns of growth of figures, pp. 215224 of R. E. Bellman, ed., Mathematical Problems in the Biological Sciences, Proc. Sympos. Applied Math., Vol. 14, Amer. Math. Soc., 1962.
S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 928.


LINKS

N. J. A. Sloane, Table of n, a(n) for n = 0..10000
David Applegate, The movie version
David Applegate, Omar E. Pol and N. J. A. Sloane, The Toothpick Sequence and Other Sequences from Cellular Automata, Congressus Numerantium, Vol. 206 (2010), 157191. [There is a typo in Theorem 6: (13) should read u(n) = 4.3^(wt(n1)1) for n >= 2.]
Steven R. Finch, Toothpicks and Live Cells, July 21, 2015. [Cached copy, with permission of the author]
Bradley Klee, Logperiodic coloring of the first quadrant, over the chair tiling.
Omar E. Pol, Illustration of initial terms (Fig. 1: onestep rook  the current sequence), (Fig. 2: onestep bishop), (Fig. 3: overlapping squares), (Fig. 4: overlapping Xtoothpicks), (2009), (Fig. 5: overlapping circles), (2010)
Omar E. Pol, Illustration of initial terms of A139250, A160120, A147562 (overlapping figures), (2009).
D. Singmaster, On the cellular automaton of Ulam and Warburton, 2003. [Cached copy, included with permission]
N. J. A. Sloane, Illustration of terms 0 through 9
N. J. A. Sloane, Catalog of Toothpick and Cellular Automata Sequences in the OEIS
N. J. A. Sloane, On the Number of ON Cells in Cellular Automata, arXiv:1503.01168 [math.CO], 2015.
Neil Sloane and Brady Haran, Terrific Toothpick Patterns, Numberphile video (2018).
Eric Weisstein's World of Mathematics, Elementary Cellular Automaton
S. Wolfram, A New Kind of Science
Index entries for sequences related to cellular automata
Index to 2D 5Neighbor Cellular Automata
Index to Elementary Cellular Automata


FORMULA

For n>0, a(n) = 1 + 4*Sum_{k=1..n} 3^(wt(k1)1), where wt() = A000120().
From Omar E. Pol, Mar 13 2011: (Start)
a(n) = 2*A151917(n)  1, for n >= 1.
a(n) = 1 + 4*A151920(n2), for n >= 2.
(End)
It appears that a(n) = A162795(n) = A169707(n), if n is a member of A048645, otherwise a(n) < A162795(n) < A169707(n).  Omar E. Pol, Feb 20 2015
It appears that a(n) = A151920(2n2), n >= 1.  Omar E. Pol, Mar 06 2015
It appears that a(n) = (A130665(2n1)  1)/3, n >= 1.  Omar E. Pol, Mar 07 2015
a(n) = 1 + 4*(A130665(n1)  1)/3, n >= 1. Omar E. Pol, Mar 07 2015


EXAMPLE

If we label the generations of cells turned ON by consecutive numbers we get a rosetta cell pattern:
. . . . . . . . . . . . . . . . .
. . . . . . . . 4 . . . . . . . .
. . . . . . . 4 3 4 . . . . . . .
. . . . . . 4 . 2 . 4 . . . . . .
. . . . . 4 3 2 1 2 3 4 . . . . .
. . . . . . 4 . 2 . 4 . . . . . .
. . . . . . . 4 3 4 . . . . . . .
. . . . . . . . 4 . . . . . . . .
. . . . . . . . . . . . . . . . .
In the first generation, only the central "1" is ON, a(1)=1. In the next generation, we turn ON four "2", leading to a(2)=a(1)+4=5. In the third generation, four "3" are turned ON, a(3)=a(2)+4=9. In the fourth generation, each of the four wings allows three 4's to be turned ON, a(4)=a(3)+4*3=21.
From Omar E. Pol, Feb 18 2015: (Start)
Also, written as an irregular triangle T(j,k), j>=0, k>=1, in which the row lengths are the terms of A011782:
1;
5;
9, 21;
25, 37, 49, 85;
89, 101,113,149,161,197,233,341;
345,357,369,405,417,453,489,597,609,645,681,789,825,933,1041,1365;
...
The right border gives the positive terms of A002450.
(End)
It appears that T(j,k) = A162795(j,k) = A169707(j,k), if k is a power of 2, for example: it appears that the three mentioned triangles only share the elements from the columns 1, 2, 4, 8, 16, ...  Omar E. Pol, Feb 20 2015


MAPLE

Since this is the partial sum sequence of A147582, it is most easily obtained using the Maple code given in A147582.
# [x, y] coordinates of cells on
Lse := [[0, 0]] ;
# enclosing rectangle of the cells on (that is, minima and maxima in Lse)
xmin := 0 ;
xmax := 0 ;
ymin := 0 ;
ymax := 0 ;
# count neighbors of x, y which are on; return 0 if [x, y] is in L
cntnei := proc(x, y, L)
local a, p, xpt, ypt;
a := 0 ;
if not [x, y] in L then
for p in Lse do
xpt := op(1, p) ;
ypt := op(2, p) ;
if ( abs(xptx) = 1 and ypt=y ) or ( x=xpt and abs(ypty) = 1) then
a := a+1 ;
fi;
od:
fi:
RETURN(a) ;
end:
# loop over generations/steps
for stp from 1 to 10 do
Lnew := [] ;
for x from xmin1 to xmax+1 do
for y from ymin1 to ymax+1 do
if cntnei(x, y, Lse) = 1 then
Lnew := [op(Lnew), [x, y]] ;
fi;
od:
od:
for p in Lnew do
xpt := op(1, p) ;
ypt := op(2, p) ;
xmin := min(xmin, xpt) ;
xmax := max(xmax, xpt) ;
ymin := min(ymin, ypt) ;
ymax := max(ymax, ypt) ;
od:
Lse := [op(Lse), op(Lnew)] ;
print(nops(Lse)) ;


MATHEMATICA

Map[Function[Apply[Plus, Flatten[ #1]]], CellularAutomaton[{686, {2, {{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}}, {1, 1}}, {{{1}}, 0}, 200]] (* Nadia Heninger and N. J. A. Sloane, Aug 11 2009 *)
ArrayPlot /@ CellularAutomaton[{686, {2, {{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}}, {1, 1}}, {{{1}}, 0}, 16]


CROSSREFS

Cf. A000120, A139250, A147582 (number turned ON at nth step), A147610, A130665, A151920, A160120, A160410, A160414, A151917, A160164, A162795, A169707, A187220, A246331.
Sequence in context: A160720 A147552 A299776 * A162795 A255366 A269522
Adjacent sequences: A147559 A147560 A147561 * A147563 A147564 A147565


KEYWORD

nonn,nice,changed


AUTHOR

N. J. A. Sloane, based on emails from Franklin T. AdamsWatters, R. J. Mathar and David W. Wilson, Apr 29 2009


EXTENSIONS

Offset and initial terms changed by N. J. A. Sloane, Jun 07 2009
Numbers in the comment adapted to the offset by R. J. Mathar, Mar 03 2010


STATUS

approved



