

A048883


a(n) = 3^wt(n), where wt(n) = A000120(n).


50



1, 3, 3, 9, 3, 9, 9, 27, 3, 9, 9, 27, 9, 27, 27, 81, 3, 9, 9, 27, 9, 27, 27, 81, 9, 27, 27, 81, 27, 81, 81, 243, 3, 9, 9, 27, 9, 27, 27, 81, 9, 27, 27, 81, 27, 81, 81, 243, 9, 27, 27, 81, 27, 81, 81, 243, 27, 81, 81, 243, 81, 243, 243, 729, 3, 9, 9, 27, 9, 27, 27, 81, 9, 27, 27, 81, 27, 81
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OFFSET

0,2


COMMENTS

Or, a(n)=number of 1's ("live" cells) at stage n of a 2dimensional cellular automata evolving by the rule: 1 if NE+NW+S=1, else 0.
This is the oddrule cellular automaton defined by OddRule 013 (see EkhadSloaneZeilberger "OddRule Cellular Automata on the Square Grid" link).  N. J. A. Sloane, Feb 25 2015
Or, start with S=[1]; replace S by [S, 3*S]; repeat ad infinitum.
Fixed point of the morphism 1 > 13, 3 > 39, 9 > 9(27), ... = 3^k > 3^k 3^(k+1), ... starting from a(0) = 1; 1 > 13 > 1339 > = 1339399(27) > 1339399(27)399(27)9(27)(27)(81) > ..., .  Robert G. Wilson v, Jan 24 2006
Equals row sums of triangle A166453 (the square of Sierpiński's gasket, A047999).  Gary W. Adamson, Oct 13 2009
First bisection of A169697=1,5,3,19,3,. a(2n+2)+a(2n+3)=12,12,36,=12*A147610 ? Distribution of terms (in A000244): A011782=1,A000079 for first array, A000079 for second.  Paul Curtz, Apr 20 2010
a(A000225(n)) = A000244(n) and a(m) != A000244(n) for m < A000225(n).  Reinhard Zumkeller, Nov 14 2011
This sequence pertains to phenotype Punnett square mathematics. Start with X=1. Each hybrid cross involves the equation X:3X. Therefore, the ratio in the first (mono) hybrid cross is X=1:3X=3(1) or 3; or 3:1. When you move up to the next hybridization level, replace the previous cross ratio with X. X now represents 2 numbers1:3. Therefore, the ratio in the second (di) hybrid cross is X=(1:3):3X=[3(1):3(3)] or (3:9). Put it together and you get 1:3:3:9. Each time you move up a hybridization level, replace the previous ratio with X, and use the same equationX:3X to get its ratio.  John Michael Feuk, Dec 10 2011


LINKS

Reinhard Zumkeller, 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
Shalosh B. Ekhad, N. J. A. Sloane, and Doron Zeilberger, A MetaAlgorithm for Creating Fast Algorithms for Counting ON Cells in OddRule Cellular Automata, arXiv:1503.01796 [math.CO], 2015; see also the Accompanying Maple Package.
Shalosh B. Ekhad, N. J. A. Sloane, and Doron Zeilberger, OddRule Cellular Automata on the Square Grid, arXiv:1503.04249 [math.CO], 2015.
Tanya Khovanova, There are no coincidences, arXiv preprint 1410.2193 [math.CO], 2014.
Tanya Khovanova and Joshua Xiong, Nim Fractals, arXiv:1405.594291 [math.CO] (2014), p. 10.
T. Pisanski and T. W. Tucker, Growth in Repeated Truncations of Maps, Atti. Sem. Mat. Fis. Univ. Modena, Vol. 49 (2001), 167176. (preprint)
Omar E. Pol, Illustration of initial terms: Fig. 1. Neighbors of the vertices, Fig. 2. Overlapping squares, Fig. 3. Onestep bishop, (Nov 06 2009)
N. J. A. Sloane, Illustration of a(15) = 81 corresponding to number of ON cells in Oddrule 013 CA at generation 15
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, 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.
R. Stephan, Divideandconquer generating functions. I. Elementary sequences, arXiv:math/0307027 [math.CO], 2003.
Index entries for sequences related to cellular automata
Index entries for sequences that are fixed points of mappings


FORMULA

a(n) = product{k=0..log_2(n), 3^b(n, k)}, b(n, k)=coefficient of 2^k in binary expansion of n(offset 0).  Paul D. Hanna
a(n) = 3a(n/2) if n is even, else a(n)=a((n+1)/2).
G.f.: Prod_{k>=0} (1+3*x^(2^k)). The generalization k^A000120 has generating function (1 + kx)(1 + kx^2)(1 + kx^4) ...
a(n+1) = sum(i=0, n, {binomial(n, i) (mod 2)}*sum(j=0, i, {binomial(i, j) (mod 2)})).  Benoit Cloitre, Nov 16 2003
1) a(4n),a(4n+1),a(4n+2),a(4n+3)=a(n)*(period 4:repeat 1,3,3,9) ? ,a(0)=1. 2) a(n)=1,3*A147610(n). Note A147582=1,4,4,12,4,12,12,36,=1,4*A147610.  Paul Curtz, Apr 20 2010
a(0)=1, a(n) = 3*a(nA053644(n)) for n>0.  Joe Slater, Jan 31 2016


EXAMPLE

From Omar E. Pol, Jun 07 2009: (Start)
Triangle begins:
1;
3;
3,9;
3,9,9,27;
3,9,9,27,9,27,27,81;
3,9,9,27,9,27,27,81,9,27,27,81,27,81,81,243;
3,9,9,27,9,27,27,81,9,27,27,81,27,81,81,243,9,27,27,81,27,81,81,243,27,...
Or
1;
3,3;
9,3,9,9;
27,3,9,9,27,9,27,27;
81,3,9,9,27,9,27,27,81,9,27,27,81,27,81,81;
243,3,9,9,27,9,27,27,81,9,27,27,81,27,81,81,243,9,27,27,81,27,81,81,243,27...
(End)


MATHEMATICA

Nest[ Join[#, 3#] &, {1}, 6] (* Robert G. Wilson v, Jan 24 2006 and modified Jul 27 2014*)
a[n_] := 3^DigitCount[n, 2, 1]; Array[a, 80, 0] (* JeanFrançois Alcover, Nov 15 2017 *)


PROG

(PARI) a(n)=n=binary(n); 3^sum(i=1, #n, n[i])
(Haskell)
a048883 = a000244 . a000120  Reinhard Zumkeller, Nov 14 2011


CROSSREFS

For generating functions Prod_{k>=0} (1+a*x^(b^k)) for the following values of (a,b) see: (1,2) A000012 and A000027, (1,3) A039966 and A005836, (1,4) A151666 and A000695, (1,5) A151667 and A033042, (2,2) A001316, (2,3) A151668, (2,4) A151669, (2,5) A151670, (3,2) A048883, (3,3) A117940, (3,4) A151665, (3,5) A151671, (4,2) A102376, (4,3) A151672, (4,4) A151673, (4,5) A151674.
A generalization of A001316. Cf. A102376.
Partial sums give A130665.  David Applegate, Jun 11 2009
Cf. A000079, A122018, A166453.
Sequence in context: A266533 A151710 A160121 * A241717 A217883 A036553
Adjacent sequences: A048880 A048881 A048882 * A048884 A048885 A048886


KEYWORD

nonn,nice,easy,hear


AUTHOR

John W. Layman


EXTENSIONS

Corrected by Ralf Stephan, Jun 19 2003
Entry revised by N. J. A. Sloane, May 30 2009
Offset changed to 0, Jun 11 2009


STATUS

approved



