cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-2 of 2 results.

A049320 Non-primitive Chacon sequence: fixed under 0->0010, 1->1.

Original entry on oeis.org

0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0
Offset: 1

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Author

Keywords

Comments

A word that is pure morphic and primitive morphic, but neither uniform morphic nor pure primitive morphic. - N. J. A. Sloane, Jul 14 2018
This is A133162 on the alphabet {0,1}, instead of {1,2}. - Michel Dekking, Oct 24 2019
The [10->1]-transform of (a(n)) is the sequence A189640. - Michel Dekking, Oct 26 2019

Crossrefs

Sequences mentioned in the Allouche et al. "Taxonomy" paper, listed by example number: 1: A003849, 2: A010060, 3: A010056, 4: A020985 and A020987, 5: A191818, 6: A316340 and A273129, 18: A316341, 19: A030302, 20: A063438, 21: A316342, 22: A316343, 23: A003849 minus its first term, 24: A316344, 25: A316345 and A316824, 26: A020985 and A020987, 27: A316825, 28: A159689, 29: A049320, 30: A003849, 31: A316826, 32: A316827, 33: A316828, 34: A316344, 35: A043529, 36: A316829, 37: A010060.

Programs

  • Haskell
    a049320 n = a049320_list !! n
    a049320_list = 0 : 0 : 1 : 0 : f [0,0,1,0] where
       f xs = drop (length xs) ys ++ f ys where
         ys = concatMap ch xs
         ch 0 = [0,0,1,0]; ch 1 = [1]
    -- Reinhard Zumkeller, Aug 14 2013
  • Mathematica
    Nest[# /. 0 -> {0, 0, 1, 0}&, {0}, 4] // Flatten (* Jean-François Alcover, Oct 08 2016 *)

Extensions

Offset changed by Michel Dekking, Oct 24 2019

A133162 Trajectory of 1 under the morphism 1 -> {1,1,2,1}, 2 -> {2}.

Original entry on oeis.org

1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 1, 2, 1, 2, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 1, 2, 1, 2, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 1, 2, 1, 2, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 1, 2, 1, 1, 1, 2, 1, 1
Offset: 1

Views

Author

N. J. A. Sloane, Oct 09 2007, Oct 10 2007

Keywords

Comments

It can be shown that this is lim_{t -> oo} S_t, where S_0 = 1, S_{t+1} = S_t S_t 2 S_t.
Suggested by A131989: a(n) = length of n-th run of 1's in A131989.
For a proof of this see the Comments of A131989. - Michel Dekking, Oct 19 2019

Crossrefs

Programs

  • Mathematica
    Nest[Function[l, {Flatten[(l /. {1 -> {1,1,2,1}, 2 -> {2} })] }], {1}, 5] (* Georg Fischer, Jul 19 2019 *)

Formula

Denote the sequence by a(1), a(2), ...
Block t, that is, S_t, extends from n=1 through n=(3^(t+1)-1)/2.
Given n, to find a(n): first find t from
p = (3^t-1)/2 < n <= (3^(t+1)-1)/2.
Then if n=3^t, a(n) = 2. Otherwise, a(n) = a(n'), where
n' = n-p if n<3^t, otherwise n' = n-2p-1.
Showing 1-2 of 2 results.