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A160552 a(0)=0, a(1)=1; a(2^i+j)=2*a(j)+a(j+1) for 0 <= j < 2^i. 38
0, 1, 1, 3, 1, 3, 5, 7, 1, 3, 5, 7, 5, 11, 17, 15, 1, 3, 5, 7, 5, 11, 17, 15, 5, 11, 17, 19, 21, 39, 49, 31, 1, 3, 5, 7, 5, 11, 17, 15, 5, 11, 17, 19, 21, 39, 49, 31, 5, 11, 17, 19, 21, 39, 49, 35, 21, 39, 53, 59, 81, 127, 129, 63, 1, 3, 5, 7, 5, 11, 17, 15, 5, 11, 17, 19, 21, 39, 49, 31 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

This recurrence is patterned after the one for A152980, but without the special cases.

Sequence viewed as triangle:

.0,

.1,

.1,3,

.1,3,5,7,

.1,3,5,7,5,11,17,15,

.1,3,5,7,5,11,17,15,5,11,17,19,21,39,49,31

The rows converge to A151548.

Also the sum of the terms in the k-th row (k >= 1) is 4^(k-1). Proof by induction. - N. J. A. Sloane, Jan 21 2010

If this sequence [1, 1, 3, 1, 3, 5, 7, 1, 3, 5, 7, 5, 11, 17, 15, ...] is convolved with [1, 2, 2, 2, 2, 2, 2, ...) we obtain A139250, the toothpick sequence. Example: A139250(5) = 15 = (1, 2, 2, 2, 2) * (3, 1, 3, 1, 1). - Gary W. Adamson, May 19 2009

Starting with 1 and convolved with [1, 2, 0, 0, 0,...] = A151548. - Gary W. Adamson, Jun 04 2009

Refer to A162956 for the analogous triangle using N=3. - Gary W. Adamson, Jul 20 2009

It appears that the sums of two successive terms give the positive terms of A139251. - Omar E. Pol, Feb 18 2015

LINKS

N. J. A. Sloane, Table of n, a(n) for n = 0..16384

David Applegate, Omar E. Pol and N. J. A. Sloane, The Toothpick Sequence and Other Sequences from Cellular Automata

N. J. A. Sloane, Catalog of Toothpick and Cellular Automata Sequences in the OEIS

FORMULA

G.f.: x*(1+2*x)/(1+x) + (4*x^2/(1+2*x))*(mul(1+x^(2^k-1)+2*x^(2^k),k>=1)-1). - N. J. A. Sloane, May 23 2009, based on Gary W. Adamson's comment above and the known g.f. for A139250.

It appears that a(n) = A169708(n)/4, n >= 1. - Omar E. Pol, Feb 15 2015

It appears that a(n) = A139251(n) - a(n-1), n >= 1. - Omar E. Pol, Feb 18 2015

EXAMPLE

a(2) = a(2^1+0) = 2*a(0)+a(1) = 1, a(3) = a(2^1+1) = 2*a(1) + a(2) = 3*a(2^i) = 2*a(0) + a(1) = 1.

MAPLE

S:=proc(n) option remember; local i, j; if n <= 1 then RETURN(n); fi; i:=floor(log(n)/log(2)); j:=n-2^i; 2*S(j)+S(j+1); end; # N. J. A. Sloane, May 18 2009

H := x*(1+2*x)/(1+x) + (4*x^2/(1+2*x))*(mul(1+x^(2^k-1)+2*x^(2^k), k=1..20)-1); series(H, x, 120); # N. J. A. Sloane, May 23 2009

MATHEMATICA

Nest[Join[#, 2 # + Append[Rest@#, 1]] &, {0}, 7] (* Ivan Neretin, Feb 09 2017 *)

CROSSREFS

For the recurrence a(2^i+j) = C*a(j) + D*a(j+1), a(0) = A, a(1) = B for following values of (A B C D) see: (0 1 1 1) A118977, (1 0 1 1) A151702, (1 1 1 1) A151570, (1 2 1 1) A151571, (0 1 1 2) A151572, (1 0 1 2) A151703, (1 1 1 2) A151573, (1 2 1 2) A151574, (0 1 2 1) A160552, (1 0 2 1) A151704, (1 1 2 1) A151568, (1 2 2 1) A151569, (0 1 2 2) A151705, (1 0 2 2) A151706, (1 1 2 2) A151707, (1 2 2 2) A151708.

Cf. A152980, A139250, A139251, A151548, A160570, A151568.

Cf. A162956, A170903.

Sequence in context: A016646 A182600 A179760 * A256263 A006257 A170898

Adjacent sequences:  A160549 A160550 A160551 * A160553 A160554 A160555

KEYWORD

nonn

AUTHOR

David Applegate, May 18 2009

STATUS

approved

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Last modified February 20 20:12 EST 2018. Contains 299385 sequences. (Running on oeis4.)