A216637 - OEIS

%I #13 Mar 19 2018 04:10:46

%S 3,1,3,3,1,1,5,1,3,1,1,3,3,1,3,2,2,3,3,1,3,3,1,1,3,2,3,3,1,3,3,1,1,5,

%T 1,3,3,1,1,3,1,1,5,1,1,5,4,5,5,1,5,5,1,1,5,4,5,5,1,1,5,1,3,1,1,3,2,3,

%U 3,1,3,3,1,1,3,1,1,5,5,1,3,1,1,5,1,1,5,5,1,3,1,1,3,3,1,3,2,2,3,3,2,3,3,1,3,3,1,1,5,1,3,3,1,3,2,3,3,1,1,3,3,1,3,2,3,3,2,2,6,2

%N Kolakoski sequence by 3-words.

%C The Kolakoski sequences (A000002) can be seen as being formed from the 6-set of 3-words -> {1,1,2}, {1,2,1}, {1,2,2}, {2,1,1}, {2,1,2} and {2,2,1}. Labeling these as 1-6 gives the sequence.

%C The first 6 appears at a(129).

%e 1,2,2,1,1,2 becomes 3,1

%o (JavaScript)

%o a=new Array();

%o a[1]=1;a[2]=2;a[3]=2;cd=1;ap=3;

%o for (i=4;i<1000;i++) {

%o if (a[ap]==1) a[i]=cd; else {a[i]=cd;a[i+1]=cd;i++}

%o ap++;cd=3-cd;}

%o for(i=1;i<300;i++) {

%o b=a.splice(1,3).join();

%o switch (b) {

%o case "1,1,2": {document.write("1,");break;}

%o case "1,2,1": {document.write("2,");break;}

%o case "1,2,2": {document.write("3,");break;}

%o case "2,1,1": {document.write("4,");break;}

%o case "2,1,2": {document.write("5,");break;}

%o case "2,2,1": {document.write("6,");break;}

%o }

%o }

%Y Cf. A000002.

%K nonn

%O 1,1

%A _Jon Perry_, Sep 11 2012