1,3

Fractal sequence obtained from powers of 2.

k occurs at (2*k-1)*A000079(m), m >= 0. - Robert G. Wilson v, May 23 2006

Sequence is T^(oo)(1) where T is acting on a word w = w(1)w(2)..w(m) as follows: T(w) = "1"w(1)"2"w(2)"3"(...)"m"w(m)"m+1". For instance T(ab) = 1a2b3. Thus T(1) = 112, T(T(1)) = 1121324, T(T(T(1))) = 112132415362748. - Benoit Cloitre, Mar 02 2009

In the binary expansion of n, first swallow all zeros from the right, then add 1, and swallow the now-appearing 0 bit as well. - Ralf Stephan, Aug 22 2013

Although A264646 and this sequence initially agree in their digit-streams, they differ after 48 digits. - N. J. A. Sloane, Nov 20 2015

"[This is a] fractal because we get the same sequence after we delete from it the first appearance of all positive integers" - see Cobeli and Zaharescu link. - Robert G. Wilson v, Jun 03 2018

From Peter Munn, Jun 16 2022: (Start)

The sequence is the list of positive integers interleaved with the sequence itself. Provided the offset is suitable (which is the case here) a term of such a self-interleaved sequence is determined by the odd part of its index. Putting some of the formulas given here into words, a(n) is the position of the odd part of n in the list of odd numbers.

Applying the interleaving transform again, we get A110963.

(End)

Omitting all 1's leaves A131987 + 1. - David James Sycamore, Jul 26 2022

J.-P. Delahaye, L'arithmétique géométrique, Pour la Science, No. 360, October 2007.

Michel Rigo, Formal Languages, Automata and Numeration Systems, 2 vols., Wiley, 2014. Mentions this sequence - see "List of Sequences" in Vol. 2.

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

N. J. A. Sloane, Table of n, a(n) for n = 1..10000

J.-P. Allouche and J. Shallit, The ring of k-regular sequences, II, Theoret. Computer Sci., 307 (2003), 3-29.

Cristian Cobeli and Alexandru Zaharescu, Promenade around Pascal Triangle - Number Motives, 7 Baby-Fractal sequences of numbers.

Dale Gerdemann, Plotting Adjacent Points in A003602, Kimberling's Paraphrase, YouTube Video, 2015.

Dale Gerdemann, Plotting Adjacent Terms of A003602 Modulo Increasing Powers of 2, YouTube Video, 2015.

Douglas E. Iannucci and Urban Larsson, Game values of arithmetic functions, arXiv:2101.07608 [math.NT], 2021.

Jonas Kaiser, On the relationship between the Collatz conjecture and Mersenne prime numbers, arXiv preprint arXiv:1608.00862 [math.GM], 2016.

Clark Kimberling, Numeration systems and fractal sequences, Acta Arithmetica 73 (1995) 103-117.

Clark Kimberling, Fractal sequences

Ralf Stephan, Some divide-and-conquer sequences ...

Ralf Stephan, Table of generating functions

Matty van-Son, Palindromic sequences of the Markov spectrum, arXiv:1804.10802 [math.NT], 2018.

Eric Weisstein's World of Mathematics, Odd Part

Index entries for sequences related to binary expansion of n

a(n) = (A000265(n) + 1)/2.

a((2*k-1)*2^m) = k, for m >= 0 and k >= 1. - Robert G. Wilson v, May 23 2006

Inverse Weigh transform of A035528. - Christian G. Bower

G.f.: 1/x * Sum_{k>=0} x^2^k/(1-2*x^2^(k+1) + x^2^(k+2)). - Ralf Stephan, Jul 24 2003

a(2*n-1) = n and a(2*n) = a(n). - Pab Ter (pabrlos2(AT)yahoo.com), Oct 25 2005

a(A118413(n,k)) = A002024(n,k); = a(A118416(n,k)) = A002260(n,k); a(A014480(n)) = A001511(A014480(n)). - Reinhard Zumkeller, Apr 27 2006

Ordinal transform of A001511. - Franklin T. Adams-Watters, Aug 28 2006

a(n) = A249745(A126760(A003961(n))) = A249745(A253887(A048673(n))). That is, this sequence plays the same role for the numbers in array A135764 as A126760 does for the odd numbers in array A135765. - Antti Karttunen, Feb 04 2015 & Jan 19 2016

G.f. satisfies g(x) = g(x^2) + x/(1-x^2)^2. - Robert Israel, Apr 24 2015

a(n) = A181988(n)/A001511(n). - L. Edson Jeffery, Nov 21 2015

a(n) = A025480(n-1) + 1. - R. J. Mathar, May 19 2016

a(n) = A110963(2n-1) = A349135(4*n). - Antti Karttunen, Apr 18 2022

a(n) = (A000035(n) + n)/2, for n odd; a(n) = a(A000035(n) + n)/2), for n even. - David James Sycamore, Jul 28 2022

From Peter Munn, Jun 14 2022: (Start)

Start of table showing the interleaving with the positive integers:

n a(n) (n+1)/2 a(n/2)

1 1 1

2 1 1

3 2 2

4 1 1

5 3 3

6 2 2

7 4 4

8 1 1

9 5 5

10 3 3

11 6 6

12 2 2

(End)

A003602:=proc(n) options remember: if n mod 2 = 1 then RETURN((n+1)/2) else RETURN(procname(n/2)) fi: end proc:

seq(A003602(n), n=1..83); # Pab Ter

nmax := 83: for m from 0 to ceil(simplify(log[2](nmax))) do for k from 1 to ceil(nmax/(m+2)) do a((2*k-1)*2^m) := k od: od: seq(a(k), k=1..nmax); # Johannes W. Meijer, Feb 04 2013

A003602 := proc(n)

a := 1;

for p in ifactors(n)[2] do

if op(1, p) > 2 then

a := a*op(1, p)^op(2, p) ;

end if;

end do :

(a+1)/2 ;

end proc: # R. J. Mathar, May 19 2016

a[n_] := Block[{m = n}, While[ EvenQ@m, m /= 2]; (m + 1)/2]; Array[a, 84] (* or *)

a[1] = 1; a[n_] := a[n] = If[OddQ@n, (n + 1)/2, a[n/2]]; Array[a, 84] (* Robert G. Wilson v, May 23 2006 *)

a[n_] := Ceiling[NestWhile[Floor[#/2] &, n, EvenQ]/2]; Array[a, 84] (* Birkas Gyorgy, Apr 05 2011 *)

a003602 = {1}; max = 7; Do[b = {}; Do[AppendTo[b, {k, a003602[[k]]}], {k, Length[a003602]}]; a003602 = Flatten[b], {n, 2, max}]; a003602 (* L. Edson Jeffery, Nov 21 2015 *)

(PARI) A003602(n)=(n/2^valuation(n, 2)+1)/2; /* Joerg Arndt, Apr 06 2011 */

(Haskell)

a003602 = (`div` 2) . (+ 1) . a000265

-- Reinhard Zumkeller, Feb 16 2012, Oct 14 2010

(Haskell)

import Data.List (transpose)

a003602 = flip div 2 . (+ 1) . a000265

a003602_list = concat $ transpose [[1..], a003602_list]

-- Reinhard Zumkeller, Aug 09 2013, May 23 2013

(Scheme) (define (A003602 n) (let loop ((n n)) (if (even? n) (loop (/ n 2)) (/ (+ 1 n) 2)))) ;; Antti Karttunen, Feb 04 2015

(Python)

import math

def a(n): return (n/2**int(math.log(n - (n & n - 1), 2)) + 1)/2 # Indranil Ghosh, Apr 24 2017

(Python)

def A003602(n): return (n>>(n&-n).bit_length())+1 # Chai Wah Wu, Jul 08 2022

a(n) is the index of the column in A135764 where n appears (see also A054582).

Cf. A000079, A000265, A001511, A003603, A003961, A014577 (with offset 1, reduction mod 2), A025480, A035528, A048673, A101279, A110963, A117303, A126760, A181988, A220466, A249745, A253887, A337821 (2-adic valuation).

Cf. also A349134 (Dirichlet inverse), A349135 (sum with it), A349136 (Möbius transform), A349431, A349371 (inverse Möbius transform).

Cf. A065120, A131987.

Cf. A000035, A264646.

Sequence in context: A351040 A347374 A336934 * A351090 A265650 A181733

Adjacent sequences: A003599 A003600 A003601 * A003603 A003604 A003605

nonn,easy,nice,hear

N. J. A. Sloane, Mira Bernstein

More terms from Pab Ter (pabrlos2(AT)yahoo.com), Oct 25 2005

approved