A214317 - OEIS

%I #18 Nov 07 2020 09:41:27

%S 1,12,121,1211,12112,121121,1211212,12112121,121121211,1211212112,

%T 12112121121,121121211211,1211212112112,12112121121121,

%U 121121211211212,1211212112112121,12112121121121211,121121211211212112,1211212112112121121,12112121121121211212

%N a(n) = length-n prefix of the Fibonacci word A003842.

%H Alois P. Heinz, <a href="/A214317/b214317.txt">Table of n, a(n) for n = 1..300</a>

%p S:= proc(n) option remember;

%p       `if`(n<2, [2-n], [S(n-1)[], S(n-2)[]])

%p     end:

%p a:= proc(n) local k;

%p       for k while nops(S(k))<n do od;

%p       parse(cat(S(k)[1..n][]))

%p     end;

%p seq(a(n), n=1..30);  # _Alois P. Heinz_, Jul 19 2012

%t S = SubstitutionSystem[{1 -> {1, 2}, 2 -> {1}}, {1}, 20];

%t FromDigits[Take[#[[1]], #[[2]]]]& /@ Transpose[{S, Range[Length[S]]}] (* _Jean-François Alcover_, Nov 07 2020 *)

%Y Cf. A003842, A214318.

%K nonn

%O 1,2

%A _N. J. A. Sloane_, Jul 12 2012