A246037 -id:A246037 - cp's OEIS frontend

A246036 Expansion of (1+4x)/((1+2x)(1-4x)).

1, 6, 20, 88, 336, 1376, 5440, 21888, 87296, 349696, 1397760, 5593088, 22368256, 89481216, 357908480, 1431666688, 5726601216, 22906535936, 91625881600, 366504050688, 1466015154176, 5864062713856, 23456246661120, 93824995033088, 375299963355136, 1501199886974976, 6004799480791040, 24019198057381888

Offset: 0

N. J. A. Sloane, Aug 21 2014

Also, fourth moments of Rudin-Shapiro polynomials (see Doche, Doche-Habsieger, Ekhad papers). - Doron Zeilberger, Apr 15 2016

Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Christophe Doche, Even moments of generalized Rudin-Shapiro polynomials, Mathematics of computation 74.252 (2005): 1923-1935.
Christophe Doche and Laurent Habsieger, Moments of the Rudin-Shapiro polynomials, Journal of Fourier Analysis and Applications 10.5 (2004): 497-505.
Shalosh B. Ekhad, Explicit Generating Functions, Asymptotics, and More for the First 10 Even Moments of the Rudin-Shapiro Polynomials, Preprint, 2016.
Shalosh B. Ekhad, N. J. A. Sloane, and Doron Zeilberger, A Meta-Algorithm for Creating Fast Algorithms for Counting ON Cells in Odd-Rule Cellular Automata, arXiv:1503.01796 [math.CO], 2015; see also the Accompanying Maple Package.
Shalosh B. Ekhad, N. J. A. Sloane, and Doron Zeilberger, Odd-Rule Cellular Automata on the Square Grid, arXiv:1503.04249 [math.CO], 2015.
N. J. A. Sloane, On the No. of ON Cells in Cellular Automata, Video of talk in Doron Zeilberger's Experimental Math Seminar at Rutgers University, Feb. 05 2015: Part 1, Part 2
N. J. A. Sloane, On the Number of ON Cells in Cellular Automata, arXiv:1503.01168 [math.CO], 2015.
Index entries for sequences related to cellular automata
Index entries for linear recurrences with constant coefficients, signature (2,8).

Cf. A001045, A003683, A054881, A246037, A271494, A271495, A271496.

I:=[1,6]; [n le 2 select I[n] else 2*Self(n-1)+8*Self(n-2): n in [1..30]]; // Vincenzo Librandi, Aug 22 2014

CoefficientList[Series[(1+4x)/((1+2x)(1-4x)), {x, 0, 50}], x] (* Vincenzo Librandi, Aug 22 2014 *)

Vec((1+4*x)/((1+2*x)*(1-4*x)) + O(x^100)) \\ Colin Barker, Aug 22 2014

apply( A246036(n)=(4^(1+n)-(-2)^n)/3, [0..30]) \\ M. F. Hasler, Sep 18 2020

A246036= BinaryRecurrenceSequence(2,8,1,6)
[A246036(n) for n in range(41)] # G. C. Greubel, Mar 08 2023

a(n) = 2*a(n-1) + 8*a(n-2).
a(n) = (4^(1+n) - (-2)^n)/3. - Colin Barker, Aug 22 2014
a(n) = A054881(n+3)/8. - L. Edson Jeffery, Apr 22 2015
a(n) = A003683(n+2)/2 and the above formula follow from the explicit expression for a(n), cf. second formula. - M. F. Hasler, Sep 11 2020
a(n) = 2^n*A001045(n+2). - R. J. Mathar, Mar 08 2021

A246039 Number of odd terms in f^n, where f = (1/x+1+x)*(1/y+y)+1.

Original entry on oeis.org

1, 7, 7, 29, 7, 49, 29, 103, 7, 49, 49, 203, 29, 203, 103, 373, 7, 49, 49, 203, 49, 343, 203, 721, 29, 203, 203, 841, 103, 721, 373, 1407, 7, 49, 49, 203, 49, 343, 203, 721, 49, 343, 343, 1421, 203, 1421, 721, 2611, 29, 203, 203, 841, 203, 1421, 841, 2987, 103, 721, 721, 2987, 373, 2611, 1407, 5277

Offset: 0

N. J. A. Sloane, Aug 21 2014

nonn

This is the number of ON cells in a certain 2-D CA in which the neighborhood of a cell is defined by f, and in which a cell is ON iff there was an odd number of ON cells in the neighborhood at the previous generation.
This is the odd-rule cellular automaton defined by OddRule 575 (see Ekhad-Sloane-Zeilberger "Odd-Rule Cellular Automata on the Square Grid" link).
Run Length Transform of A246038.
The Run Length Transform of a sequence {S(n), n>=0} is defined to be the sequence {T(n), n>=0} given by T(n) = Product_i S(i), where i runs through the lengths of runs of 1's in the binary expansion of n. E.g. 19 is 10011 in binary, which has two runs of 1's, of lengths 1 and 2. So T(19) = S(1)*S(2). T(0)=1 (the empty product).

			Here is the neighborhood:
[X, X, X]
[0, X, 0]
[X, X, X]
which contains a(1) = 7 ON cells.

Alois P. Heinz, Table of n, a(n) for n = 0..8192
Shalosh B. Ekhad, N. J. A. Sloane, and Doron Zeilberger, A Meta-Algorithm for Creating Fast Algorithms for Counting ON Cells in Odd-Rule Cellular Automata, arXiv:1503.01796, 2015; see also the Accompanying Maple Package.
Shalosh B. Ekhad, N. J. A. Sloane, and Doron Zeilberger, Odd-Rule Cellular Automata on the Square Grid, arXiv:1503.04249, 2015.
N. J. A. Sloane, On the No. of ON Cells in Cellular Automata, Video of talk in Doron Zeilberger's Experimental Math Seminar at Rutgers University, Feb. 05 2015: Part 1, Part 2
N. J. A. Sloane, On the Number of ON Cells in Cellular Automata, arXiv:1503.01168, 2015
Index entries for sequences related to cellular automata

Other CA's that use the same rule but with different cell neighborhoods: A160239, A102376, A071053, A072272, A001316, A246034, A246035. A246037.

Cf. A246038.

C:=f->subs({x=1, y=1}, f);
# Find number of ON cells in CA for generations 0 thru M defined by rule
# that cell is ON iff number of ON cells in nbd at time n-1 was odd
# where nbd is defined by a polynomial or Laurent series f(x, y).
OddCA:=proc(f, M) global C; local n, a, i, f2, p;
f2:=simplify(expand(f)) mod 2;
a:=[]; p:=1;
for n from 0 to M do a:=[op(a), C(p)]; p:=expand(p*f2) mod 2; od:
lprint([seq(a[i], i=1..nops(a))]);
end;
f:=(1/x+1+x)*(1/y+y)+1 mod 2;
OddCA(f, 70);

(* f = A246038 *) f[0]=1; f[1]=7; f[2]=29; f[3]=103; f[4]=373; f[n_] := f[n] = 8 f[n-4] + 8 f[n-3] + 3 f[n-1]; Table[Times @@ (f[Length[#]]&) /@ Select[Split[IntegerDigits[n, 2]], #[[1]] == 1&], {n, 0, 63}] (* Jean-François Alcover, Jul 12 2017 *)

A246314 Number of odd terms in f^n, where f = 1/x^2+1/x+1+x+x^2+1/y^2+1/y+y+y^2.

Original entry on oeis.org

1, 9, 9, 37, 9, 65, 37, 157, 9, 81, 65, 237, 37, 293, 157, 713, 9, 81, 81, 333, 65, 473, 237, 1077, 37, 333, 293, 1129, 157, 1285, 713, 2737, 9, 81, 81, 333, 81, 585, 333, 1413, 65, 585, 473, 1733, 237, 1933, 1077, 4337, 37, 333, 333, 1369, 293, 2125, 1129, 4969, 157, 1413, 1285, 5041, 713, 5561, 2737, 11421, 9, 81

Offset: 0

N. J. A. Sloane, Aug 26 2014

nonn

This is the number of ON cells in a certain 2-D CA in which the neighborhood of a cell is defined by f (a cross containing 9 cells), and in which a cell is ON iff there was an odd number of ON cells in the neighborhood at the previous generation.

			Here is the neighborhood:
[0, 0, X, 0, 0]
[0, 0, X, 0, 0]
[X, X, X, X, X]
[0, 0, X, 0, 0]
[0, 0, X, 0, 0]
which contains a(1) = 9 ON cells.
The second and third generations are:
[0, 0, 0, 0, X, 0, 0, 0, 0]
[0, 0, 0, 0, 0, 0, 0, 0, 0]
[0, 0, 0, 0, X, 0, 0, 0, 0]
[0, 0, 0, 0, 0, 0, 0, 0, 0]
[X, 0, X, 0, X, 0, X, 0, X]  (again with 9 ON cells)
[0, 0, 0, 0, 0, 0, 0, 0, 0]
[0, 0, 0, 0, X, 0, 0, 0, 0]
[0, 0, 0, 0, 0, 0, 0, 0, 0]
[0, 0, 0, 0, X, 0, 0, 0, 0]
[0, 0, 0, 0, 0, 0, X, 0, 0, 0, 0, 0, 0]
[0, 0, 0, 0, 0, 0, X, 0, 0, 0, 0, 0, 0]
[0, 0, 0, 0, X, X, 0, X, X, 0, 0, 0, 0]
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
[0, 0, X, 0, 0, X, X, X, 0, 0, X, 0, 0]
[0, 0, X, 0, X, 0, 0, 0, X, 0, X, 0, 0]
[X, X, 0, 0, X, 0, X, 0, X, 0, 0, X, X] (with 37 ON cells)
[0, 0, X, 0, X, 0, 0, 0, X, 0, X, 0, 0]
[0, 0, X, 0, 0, X, X, X, 0, 0, X, 0, 0]
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
[0, 0, 0, 0, X, X, 0, X, X, 0, 0, 0, 0]
[0, 0, 0, 0, 0, 0, X, 0, 0, 0, 0, 0, 0]
[0, 0, 0, 0, 0, 0, X, 0, 0, 0, 0, 0, 0]
The terms can be arranged into blocks of sizes 1,1,2,4,8,16,32,...:
1,
9,
9, 37,
9, 65, 37, 157,
9, 81, 65, 237, 37, 293, 157, 713,
9, 81, 81, 333, 65, 473, 237, 1077, 37, 333, 293, 1129, 157, 1285, 713, 2737,
9, 81, 81, 333, 81, 585, 333, 1413, 65, 585, 473, 1733, 237, 1933, 1077, 4337, 37, 333, 333, 1369, 293, 2125, 1129, 4969, 157, 1413, 1285, 5041, 713, 5561, 2737, 11421, ...
The final terms in the rows are A246315.

Alois P. Heinz, Table of n, a(n) for n = 0..512

Other CA's that use the same rule but with different cell neighborhoods: A160239, A102376, A071053, A072272, A001316, A246034, A246035, A246037.

Cf. A246315, A247647, A247648, A247649.

C:=f->subs({x=1, y=1}, f);
# Find number of ON cells in CA for generations 0 thru M defined by rule
# that cell is ON iff number of ON cells in nbd at time n-1 was odd
# where nbd is defined by a polynomial or Laurent series f(x, y).
OddCA:=proc(f, M) global C; local n, a, i, f2, p;
f2:=simplify(expand(f)) mod 2;
a:=[]; p:=1;
for n from 0 to M do a:=[op(a), C(p)]; p:=expand(p*f2) mod 2; od:
lprint([seq(a[i], i=1..nops(a))]);
end;
f:=1/x^2+1/x+1+x+x^2+1/y^2+1/y+y+y^2;
OddCA(f, 70);

c[f_] := f /. {x -> 1, y -> 1};
OddCA[f_, M_] := Module[{a = {}, f2, p = 1}, f2 = PolynomialMod[f, 2]; Do[ AppendTo[a, c[p]]; Print[a]; p = PolynomialMod[p f2, 2], {n, 0, M}]; a];
f = 1/x^2 + 1/x + 1 + x + x^2 + 1/y^2 + 1/y + y + y^2;
OddCA[f, 70] (* Jean-François Alcover, May 24 2020, after Maple *)

The values of a(n) for n in A247647 (or A247648) determine all the values, as follows. Parse the binary expansion of n into terms from A247647 separated by at least two zeros: m_1 0...0 m_2 0...0 m_3 ... m_r 0...0. Ignore any number (one or more) of trailing zeros. Then a(n) = a(m_1)*a(m_2)*...*a(m_r). For example, n = 37_10 = 100101_2 is parsed into 1.00.101, and so a(37) = a(1)*a(5) = 9*65 = 585. This is a generalization of the Run Length Transform.

cp's OEIS Frontend

A246036 Expansion of (1+4x)/((1+2x)(1-4x)).

Views

Author

Keywords

Comments

Links

Crossrefs

Programs

Magma

Mathematica

PARI

PARI

SageMath

Formula

A246039 Number of odd terms in f^n, where f = (1/x+1+x)*(1/y+y)+1.

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Programs

Maple

Mathematica

A246314 Number of odd terms in f^n, where f = 1/x^2+1/x+1+x+x^2+1/y^2+1/y+y+y^2.

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Programs

Maple

Mathematica

Formula

cp's OEIS Frontend

A246036 Expansion of (1+4*x)/((1+2*x)*(1-4*x)).

Views

Author

Keywords

Comments

Links

Crossrefs

Programs

Magma

Mathematica

PARI

PARI

SageMath

Formula

A246039 Number of odd terms in f^n, where f = (1/x+1+x)*(1/y+y)+1.

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Programs

Maple

Mathematica

A246314 Number of odd terms in f^n, where f = 1/x^2+1/x+1+x+x^2+1/y^2+1/y+y+y^2.

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Programs

Maple

Mathematica

Formula

A246036 Expansion of (1+4x)/((1+2x)(1-4x)).