A288711 - OEIS

%I #30 Apr 06 2020 20:09:23

%S 1,0,0,0,0,0,1,0,0,0,0,0,1,0,0,0,1,0,0,0,0,0,1,0,0,0,0,0,1,0,0,0,1,0,

%T 0,0,0,0,1,0,0,0,1,0,0,0,0,0,1,0,0,0,0,0,1,0,0,0,1,0,0,0,0,0,1,0,0,0,

%U 0,0,1,0,0,0,1,0,0,0,0,0,1,0,0,0,1,0

%N 1-limiting word of the mapping 00->1000, 10->00, starting with 00.

%C Iterates of the mapping, starting with 00:

%C 00

%C 1000

%C 001000

%C 1000001000

%C 0010001000001000

%C 10000010000010001000001000

%C 001000100000100010000010000010001000001000

%C The 1-limiting word is the limit of the n-th iterates for n == 1 mod 2.

%C The number of letters (0's and 1's) in the n-th iterate is given by 2*F(n+2) for n >= 0, where F = A000045 (Fibonacci numbers), as follows from the observation that this sequence is the {0->00, 1->10}-transform of the mapping 0->10, 1->0; see the Example section.

%H Clark Kimberling, <a href="/A288711/b288711.txt">Table of n, a(n) for n = 1..10000</a>

%e The first three n-th iterates for n == 1 (mod 3) are

%e 1000

%e 1000001000

%e 10000010000010001000001000

%e Regarding the connection to Fibonacci numbers mentioned in Comments, iterates of the morphism 0->10, 1->0, starting with 0th iterate 0, are

%e 0

%e 10

%e 010

%e 10010

%e 01010010

%e 1001001010010

%e where the length of the n-th iterate is F(n+2). The {0->00, 1->10}-transform of the iterates is then 00, 1000, 001000, ..., as indicated in Comments.

%t s = {0, 0}; w[0] = StringJoin[Map[ToString, s]];

%t w[n_] := StringReplace[w[n - 1], {"00" -> "1000", "10" -> "00"}]

%t Table[w[n], {n, 0, 8}]

%t st = ToCharacterCode[w[9]] - 48   (* A288711 *)

%t Flatten[Position[st, 0]]  (* A288712 *)

%t Flatten[Position[st, 1]]  (* A288713 *)

%t Table[StringLength[w[n]], {n, 0, 20}] (* 2*A000045 *)

%Y Cf. A000045, A288708, A288709.

%K nonn,easy

%O 1

%A _Clark Kimberling_, Jun 16 2017