A151906 -id:A151906 - cp's OEIS frontend

A151907 Partial sums of A151906.

0, 1, 5, 9, 13, 25, 29, 33, 45, 57, 69, 105, 109, 113, 125, 137, 149, 185, 197, 209, 245, 281, 317, 425, 429, 433, 445, 457, 469, 505, 517, 529, 565, 601, 637, 745, 757, 769, 805, 841, 877, 985, 1021, 1057, 1165, 1273, 1381, 1705, 1709, 1713, 1725, 1737, 1749, 1785, 1797

Offset: 0

David Applegate and N. J. A. Sloane, Jul 31 2009, Aug 03 2009

nonn

a(n) is the total number of ON cells after n generations in the Holladay-Ulam CA shown in Fig. 2 and Example 2 of the Ulam article.
The definition of this CA given by Ulam on pp. 216, 222 is complicated (and incomplete). However, the same structure can be obtained as follows. Take the CA of A147562 but replace each square by a Maltese cross, a cluster of five adjacent squares:
..X..
.XXX.
..X..
We guess that this was how Holladay and Ulam originally constructed the CA.
This construction corresponds to the fact that the three trisections of the difference sequence A151906 are essentially A147582, A147582 and 3*A147582 respectively.

S. Ulam, On some mathematical problems connected with patterns of growth of figures, pp. 215-224 of R. E. Bellman, ed., Mathematical Problems in the Biological Sciences, Proc. Sympos. Applied Math., Vol. 14, Amer. Math. Soc., 1962.

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), 157-191. [There is a typo in Theorem 6: (13) should read u(n) = 4.3^(wt(n-1)-1) for n >= 2.]
N. J. A. Sloane, Catalog of Toothpick and Cellular Automata Sequences in the OEIS
N. J. A. Sloane, Illustration of initial terms (annotated copy of figure on p. 222 of Ulam)

Cf. A151904, A151905, A151906, A139250, A151895, A151896.

The definition in terms of A151906 provides an explicit formula for a(n).

A151895 Number of ON cells after n generations of the cellular automaton on the square grid that is described in the Comments.

Original entry on oeis.org

0, 1, 5, 9, 13, 25, 29, 41, 53, 65, 85, 97, 117, 145, 149, 161, 173, 185, 213, 233, 261, 297, 333, 385, 429, 481, 533, 545, 573, 601, 629, 673, 717, 761, 837, 905, 989, 1033, 1085, 1145, 1197, 1257, 1309, 1337, 1397, 1457, 1525, 1625, 1669

Offset: 0

David Applegate and N. J. A. Sloane, Jul 30 2009

nonn

The cells are the squares of the standard square grid.
Cells are either OFF or ON, once they are ON they stay ON, and we begin in generation 1 with 1 ON cell.
Each cell has 4 neighbors, those that it shares an edge with. Cells that are ON at generation n all try simultaneously to turn ON all their neighbors that are OFF. They can only do this at this point in time; afterwards they go to sleep (but stay ON).
A square Q is turned ON at generation n+1 if:
a) Q shares an edge with one and only one square P (say) that was turned ON at generation n (in which case the two squares which intersect Q only in a vertex not on that edge are called Q's "outer squares"), and
b) Q's outer squares were not considered (that is, satisfied a)) in any previous generation, and
c) Q's outer squares are not prospective squares of the (n+1)st generation satisfying a).
Originally constructed in an attempt to explain the Holladay-Ulam CA shown in Fig. 2 of the 1962 Ulam article. However, as explained on page 222 of that article, the actual rule for that CA (see A151906, A151907) is different from ours.
A170896 and A267190 are also closely related cellular automata.
A151895 and A267190 first differ at n=17, when A267190 turns (12,2) ON even though its outer square (11,1) was considered (not turned ON) in a previous generation. - David Applegate, Jan 30 2016

D. Applegate, Omar E. Pol and N. J. A. Sloane, The Toothpick Sequence and Other Sequences from Cellular Automata, Congressus Numerantium, Vol. 206 (2010), 157-191.

David Applegate, Table of n, a(n) for n = 0..250
David Applegate, The movie version
David Applegate, Illustration of first 10 generations
David Applegate, Illustration of first 20 generations
David Applegate, Illustration of first 32 generations
David Applegate, Illustration of first 64 generations
David Applegate, Omar E. Pol and N. J. A. Sloane, The Toothpick Sequence and Other Sequences from Cellular Automata, Congressus Numerantium, Vol. 206 (2010), 157-191. [There is a typo in Theorem 6: (13) should read u(n) = 4.3^(wt(n-1)-1) for n >= 2.], which is also available at arXiv:1004.3036v2
R. G. Schrandt and S. M. Ulam, On recursively defined geometric objects and patterns of growth [Link supplied by Laurinda J. Alcorn, Jan 09 2010.]
N. J. A. Sloane, Illustration of initial terms (concentrating on a 90-degree sector)
N. J. A. Sloane, Catalog of Toothpick and Cellular Automata Sequences in the OEIS
S. M. Ulam, On some mathematical problems connected with patterns of growth of figures, pp. 215-224 of R. E. Bellman, ed., Mathematical Problems in the Biological Sciences, Proc. Sympos. Applied Math., Vol. 14, Amer. Math. Soc., 1962 [Annotated scanned copy]

See A170896, A170897 for the original Schrandt-Ulam version.

Cf. A151896 (the first differences), A139250, A151905, A151906, A151907, A267190, A267191.

We do not know of a recurrence or generating function.

Entry (including definition) revised by David Applegate and N. J. A. Sloane, Jan 21 2016

A170896 Number of ON cells after n generations of the Schrandt-Ulam cellular automaton on the square grid that is described in the Comments.

Original entry on oeis.org

0, 1, 5, 9, 13, 25, 29, 41, 53, 65, 85, 97, 117, 145, 157, 169, 181, 201, 229, 249, 285, 321, 365, 409, 445, 497, 549, 577, 605, 633, 669, 713, 757, 825, 893, 969, 1045, 1105, 1173, 1241, 1309, 1377, 1437, 1473, 1541, 1609, 1693, 1793, 1869, 1945, 2037, 2105, 2189, 2281, 2381, 2521, 2621, 2753, 2869, 2969, 3053, 3129, 3237, 3377, 3485, 3585, 3685, 3817, 3909

Offset: 0

N. J. A. Sloane, Jan 09 2010

nonn

The cells are the squares of the standard square grid.
Cells are either OFF or ON, once they are ON they stay ON, and we begin in generation 1 with 1 ON cell.
Each cell has 4 neighbors, those that it shares an edge with. Cells that are ON at generation n all try simultaneously to turn ON all their neighbors that are OFF. They can only do this at this point in time; afterwards they go to sleep (but stay ON).
A square Q is turned ON at generation n+1 if:
a) Q shares an edge with one and only one square P (say) that was turned ON at generation n (in which case the two squares which intersect Q only in a vertex not on that edge are called Q's "outer squares"), and
b) Q's outer squares were not turned ON in any previous generation.
c) In addition, of this set of prospective squares of the (n+1)th generation satisfying the previous condition, we eliminate all squares which are outer squares of other prospective squares.
A151895, A151906, and A267190 are closely related cellular automata.

D. Applegate, Omar E. Pol and N. J. A. Sloane, The Toothpick Sequence and Other Sequences from Cellular Automata, Congressus Numerantium, Vol. 206 (2010), 157-191.

David Applegate, Table of n, a(n) for n = 0..260 (corrected by Sean A. Irvine)
David Applegate, The movie version
David Applegate, After 20 generations, illustrating a(20)=285 (with the A170897(20)=36 newly created cells shown in blue)
David Applegate, After 26 generations, illustrating a(26)=549 (with the A170897(26)=52 newly created cells shown in blue)
David Applegate, Omar E. Pol and N. J. A. Sloane, The Toothpick Sequence and Other Sequences from Cellular Automata, Congressus Numerantium, Vol. 206 (2010), 157-191. [There is a typo in Theorem 6: (13) should read u(n) = 4.3^(wt(n-1)-1) for n >= 2.]
Sean A. Irvine, Java program (github)
R. G. Schrandt and S. M. Ulam, On recursively defined geometric objects and patterns of growth [Link supplied by Laurinda J. Alcorn, Jan 09 2010.]
N. J. A. Sloane, Catalog of Toothpick and Cellular Automata Sequences in the OEIS
N. J. A. Sloane, Exciting Number Sequences (video of talk), Mar 05 2021
S. M. Ulam, On some mathematical problems connected with patterns of growth of figures, pp. 215-224 of R. E. Bellman, ed., Mathematical Problems in the Biological Sciences, Proc. Sympos. Applied Math., Vol. 14, Amer. Math. Soc., 1962 [Annotated scanned copy]

Cf. A139250, A170897 (first differences), A151895, A151896, A151906, A267190.

We do not know of a recurrence or generating function.

Entry (including definition) revised by David Applegate and N. J. A. Sloane, Jan 21 2016

A296511 Number of toothpicks added at n-th stage to the toothpick structure of A296510.

Original entry on oeis.org

1, 2, 4, 6, 6, 6, 6, 10, 16, 20, 16, 10, 6, 10, 16, 24, 28, 32, 28, 32, 40, 50, 40, 22, 8, 10, 16, 24, 28, 32, 32, 40, 56, 74, 76, 64, 42, 36, 40, 62, 76, 90, 80, 88, 102, 122, 96, 50, 14, 10, 16, 24, 28, 32, 32, 40, 56, 74, 76, 64, 46, 44, 56, 82, 104, 124

Offset: 1

Omar E. Pol, Dec 14 2017

The structure and the behavior of this cellular automaton reveals that some cellular automata have recurrent periods that can be represented by irregular triangles of first differences whose row lengths are the terms of A011782 multiplied by k (instead of powers of 2), where k is the length of their "word". In this case the word must be "abc", therefore k = 3. In the case of the cellular automaton with normal toothpicks (A139250) the word must be "ab" and k = 2.
The associated sound to the animation of this cellular automaton could be [tick, tock, tack], [tic, tock, tack], and so on.
For more information about the "word" of a cellular automaton see A296612.

			The structure of this irregular triangle is as shown below:
   a, b, c;
   a, b, c;
   a, b, c, a, b, c;
   a, b, c, a, b, c, a, b, c, a, b, c;
   a, b, c, a, b, c, a, b, c, a, b, c, a, b, c, a, b, c, a, b, c, a, b, c;
...
Every column is associated successively to one of the axes of the triangular grid.
Every row represents a geometric period of the cellular automaton.
So, written as an irregular triangle in which the row lengths are the terms of A011782 multiplied by 3, the sequence begins:
   1, 2, 4;
   6, 6, 6;
   6,10,16,20,16,10;
   6,10,16,24,28,32,28,32,40,50,40,22;
   8,10,16,24,28,32,32,40,56,74,76,64,42,36,40,62,76,90,80,88,102,122,96,50;
  14,10,16,24,28,32,32,40,56,74,76,64,...
...

Rémy Sigrist, Table of n, a(n) for n = 1..6144
Rémy Sigrist, Illustration of the construction at generation 3*256
Rémy Sigrist, PARI program
N. J. A. Sloane, Catalog of Toothpick and Cellular Automata Sequences in the OEIS
Index entries for sequences related to cellular automata
Index entries for sequences related to toothpick sequences

First differences of A296510.
Cf. A160121 (word "a"), A139251 (word "ab"), A299477 (word "abcb"), A299479 (word "abcbc").
Cf. A007283, A011782, A151906, A160121, A160161, A292612.

PARI
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See Links section.
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More terms from Rémy Sigrist, Jul 22 2022

A151905 a(0) = a(2) = 0, a(1) = 1; for n >= 3, n = 32^k+j, 0 <= j < 32^k, a(n) = A151904(j).

Original entry on oeis.org

0, 1, 0, 0, 0, 1, 0, 0, 1, 1, 1, 4, 0, 0, 1, 1, 1, 4, 1, 1, 4, 4, 4, 13, 0, 0, 1, 1, 1, 4, 1, 1, 4, 4, 4, 13, 1, 1, 4, 4, 4, 13, 4, 4, 13, 13, 13, 40, 0, 0, 1, 1, 1, 4, 1, 1, 4, 4, 4, 13, 1, 1, 4, 4, 4, 13, 4, 4, 13, 13, 13, 40, 1, 1, 4, 4, 4, 13, 4, 4, 13, 13, 13, 40, 4, 4, 13, 13, 13, 40, 13

Offset: 0

N. J. A. Sloane, Jul 31 2009

Consider the Holladay-Ulam CA shown in Fig. 2 and Example 2 of the Ulam article. Then a(n) is the number of cells turned ON in generation n in a 45-degree sector that are not on the main stem.

			If written as a triangle:
0,
1, 0,
0, 0, 1,
0, 0, 1, 1, 1, 4,
0, 0, 1, 1, 1, 4, 1, 1, 4, 4, 4, 13,
0, 0, 1, 1, 1, 4, 1, 1, 4, 4, 4, 13, 1, 1, 4, 4, 4, 13, 4, 4, 13, 13, 13, 40
0, 0, 1, 1, 1, 4, 1, 1, 4, 4, 4, 13, 1, 1, 4, 4, 4, 13, 4, 4, 13, 13, 13, 40, 1, 1, 4, 4, 4, 13, 4, 4, 13, 13, 13, 40, 4, 4, 13, 13, 13, 40, 13, 13, 40, 40, 40, 121,
...
then the rows converge to A151904.

S. Ulam, On some mathematical problems connected with patterns of growth of figures, pp. 215-224 of R. E. Bellman, ed., Mathematical Problems in the Biological Sciences, Proc. Sympos. Applied Math., Vol. 14, Amer. Math. Soc., 1962.

David Applegate, Omar E. Pol and N. J. A. Sloane, The Toothpick Sequence and Other Sequences from Cellular Automata, Congressus Numerantium, Vol. 206 (2010), 157-191. [There is a typo in Theorem 6: (13) should read u(n) = 4.3^(wt(n-1)-1) for n >= 2.]
N. J. A. Sloane, Catalog of Toothpick and Cellular Automata Sequences in the OEIS
N. J. A. Sloane, Illustration of initial terms (annotated copy of figure on p. 222 of Ulam)

Cf. A151904, A151906, A151907, A139250, A151895, A151896.

f := proc(n) local j; j:=n mod 6; if (j<=1) then 0 elif (j<=4) then 1 else 2; fi; end;
wt := proc(n) local w,m,i; w := 0; m := n; while m > 0 do i := m mod 2; w := w+i; m := (m-i)/2; od; w; end;
A151904 := proc(n) local k,j; k:=floor(n/6); j:=n-6*k; (3^(wt(k)+f(j))-1)/2; end;
A151905 := proc (n) local k,j;
if (n=0) then 0;
elif (n=1) then 1;
elif (n=2) then 0;
else k:=floor( log(n/3)/log(2) ); j:=n-3*2^k; A151904(j); fi;
end;

wt[n_] := DigitCount[n, 2, 1];
f[n_] := {0, 0, 1, 1, 1, 2}[[Mod[n, 6] + 1]];
A151902[n_] := wt[Floor[n/6]] + f[n - 6 Floor[n/6]];
A151904[n_] := (3^A151902[n] - 1)/2;
a[n_] := Module[{k, j}, Switch[n, 0, 0, 1, 1, 2, 0, _, k = Floor[Log2[n/3]]; j = n - 3*2^k; A151904[j]]];
Table[a[n], {n, 0, 90}] (* Jean-François Alcover, Feb 16 2023, after Maple code *)

A267190 Number of ON cells after n generations of the cellular automaton on the square grid that is described in the Comments.

Original entry on oeis.org

0, 1, 5, 9, 13, 25, 29, 41, 53, 65, 85, 97, 117, 145, 149, 161, 173, 193, 221, 241, 277, 313, 357, 401, 437, 489, 541, 553, 581, 609, 645, 689, 733, 801, 869, 945, 1021, 1081, 1149, 1217, 1277, 1345, 1397, 1433, 1501, 1569, 1653, 1753, 1829, 1905, 1997, 2057, 2141, 2225, 2317, 2449, 2549, 2681, 2797, 2889, 2965, 3041, 3149, 3289

Offset: 0

David Applegate and N. J. A. Sloane, Jan 21 2016

nonn

The cells are the squares of the standard square grid.
Cells are either OFF or ON, once they are ON they stay ON, and we begin in generation 1 with 1 ON cell.
Each cell has 4 neighbors, those that it shares an edge with. Cells that are ON at generation n all try simultaneously to turn ON all their neighbors that are OFF. They can only do this at this point in time; afterwards they go to sleep (but stay ON).
A square Q is turned ON at generation n+1 if:
a) Q shares an edge with one and only one square P (say) that was turned ON at generation n (in which case the two squares which intersect Q only in a vertex not on that edge are called Q's “outer squares”), and
b) Q's outer squares were not turned ON in any previous generation, and
c) Q's outer squares are not prospective squares of the (n+1)st generation satisfying a).
A151895, A151906, and A170896 are closely related cellular automata.
The key difference between this and A170896 is that if we have two squares Q1 and Q2, both satisfying a), and that are each an outer square of the other, where Q1 satisfies b), but Q2 does not, then for A170896 Q1 is accepted, but for this sequence Q1 is eliminated.  This first happens at n=14, when, for example, A170896 turns (8,3) ON but A267190 doesn't (because (9,2) fails to satisfy b) because (8,1) is ON). - David Applegate, Jan 30 2016
A151895 and A267190 first differ at n=17, when A267190 turns (12,2) ON even though its outer square (11,1) was considered (not turned ON) in a previous generation. - David Applegate, Jan 30 2016

D. Applegate, Omar E. Pol and N. J. A. Sloane, The Toothpick Sequence and Other Sequences from Cellular Automata, Congressus Numerantium, Vol. 206 (2010), 157-191

David Applegate, Table of n, a(n) for n = 0..260
David Applegate, The movie version
David Applegate, After 16 generations, illustrating a(16)=173 (with the A267191(16)=12 newly created cells shown in blue)
David Applegate, After 36 generations, illustrating a(36)=1021 (with the A267191(36)=76 newly created cells shown in blue) David Applegate, Omar E. Pol and N. J. A. Sloane, The Toothpick Sequence and Other Sequences from Cellular Automata, Congressus Numerantium, Vol. 206 (2010), 157-191. [There is a typo in Theorem 6: (13) should read u(n) = 4.3^(wt(n-1)-1) for n >= 2.], which is also available at arXiv:1004.3036v2
S. M. Ulam, On some mathematical problems connected with patterns of growth of figures, pp. 215-224 of R. E. Bellman, ed., Mathematical Problems in the Biological Sciences, Proc. Sympos. Applied Math., Vol. 14, Amer. Math. Soc., 1962 [Annotated scanned copy]
Index entries for sequences related to toothpick sequences
Index entries for sequences related to cellular automata

Cf. A267191 (first differences), A151895, A151906, A170896.

A151899 Period 6: repeat [0, 0, 1, 1, 1, 2].

Original entry on oeis.org

0, 0, 1, 1, 1, 2, 0, 0, 1, 1, 1, 2, 0, 0, 1, 1, 1, 2, 0, 0, 1, 1, 1, 2, 0, 0, 1, 1, 1, 2, 0, 0, 1, 1, 1, 2, 0, 0, 1, 1, 1, 2, 0, 0, 1, 1, 1, 2, 0, 0, 1, 1, 1, 2, 0, 0, 1, 1, 1, 2, 0, 0, 1, 1, 1, 2, 0, 0, 1, 1, 1, 2, 0, 0, 1, 1, 1, 2, 0, 0, 1, 1, 1, 2, 0, 0, 1, 1, 1, 2, 0, 0, 1, 1, 1, 2, 0, 0, 1, 1, 1, 2, 0, 0, 1

Offset: 0

N. J. A. Sloane, Jul 31 2009

Index entries for linear recurrences with constant coefficients, signature (0,0,0,0,0,1).

Cf. A151902, A151904, A151905, A151906, A151907.

[Abs( ((1-n) mod 3) - ((1+n) mod 2) ) : n in [0..100]]; // Wesley Ivan Hurt, Aug 20 2014

f := proc(n) local j; j:=n mod 6; if (j<=1) then 0 elif (j<=4) then 1 else 2; fi; end;
A151899:=n->[0, 0, 1, 1, 1, 2][(n mod 6)+1]: seq(A151899(n), n=0..100); # Wesley Ivan Hurt, Jun 20 2016

Table[Abs[Mod[-n + 1, 3] - Mod[n + 1, 2]], {n, 0, 100}] (* Wesley Ivan Hurt, Aug 20 2014 *)
CoefficientList[Series[(x^2 + x^3 + x^4 + 2 x^5)/(1 - x^6), {x, 0, 100}], x] (* Wesley Ivan Hurt, Aug 20 2014 *)
LinearRecurrence[{0, 0, 0, 0, 0, 1},{0, 0, 1, 1, 1, 2},105] (* Ray Chandler, Aug 26 2015 *)

a(n)=[0,0,1,1,1,2][n%6+1]; \\ Joerg Arndt, Aug 25 2014

a(n) = 5/6 - cos(Pi*n/3)/3 - sin(Pi*n/3)/sqrt(3) - cos(2*Pi*n/3)/3 - sin(2*Pi*n/3)/sqrt(3) - (-1)^n/6. - R. J. Mathar, Oct 08 2011
G.f.: (x^2+x^3+x^4+2*x^5)/(1-x^6); a(n) = abs( mod(1-n,3) - mod(1+n,2) ). - Wesley Ivan Hurt, Aug 20 2014
a(n) = a(n-6) for n>5. - Wesley Ivan Hurt, Jun 20 2016

cp's OEIS Frontend

A151907 Partial sums of A151906.

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A151895 Number of ON cells after n generations of the cellular automaton on the square grid that is described in the Comments.

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A170896 Number of ON cells after n generations of the Schrandt-Ulam cellular automaton on the square grid that is described in the Comments.

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A296511 Number of toothpicks added at n-th stage to the toothpick structure of A296510.

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PARI

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A151905 a(0) = a(2) = 0, a(1) = 1; for n >= 3, n = 3*2^k+j, 0 <= j < 3*2^k, a(n) = A151904(j).

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A267190 Number of ON cells after n generations of the cellular automaton on the square grid that is described in the Comments.

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A151899 Period 6: repeat [0, 0, 1, 1, 1, 2].

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A151905 a(0) = a(2) = 0, a(1) = 1; for n >= 3, n = 32^k+j, 0 <= j < 32^k, a(n) = A151904(j).