Collatz Sequence on Cyclic Tag System in JavaScript/Node.js

cts-Collatz.js

// Collatz Sequence on 2-tag system
// rule: {A -> BC, B -> A, C -> AAA}, value: AAA for 3, for example

// Translation from 2-tag system to cyclic tag system
const A = "100", B = "010", C = "001", S = " ";
const clist = [B+C, A, A+A+A, S, S, S];

function printn(q) {
    let n = 0;
    while (q.length != 0 && q.slice(0, 3) == A) {
        n += 1; q = q.slice(3);
    }
    if (q.length == 0 && n % 2 != 0) console.log(n);
}

const n = 39;

let queue = A.repeat(n), ci = 0;
printn(queue);
while (queue.length > 3) {
    if (queue[0] == '1' && clist[ci] != S) queue += clist[ci];
    queue = queue.slice(1);
    ci = (ci + 1) % clist.length;
    if (ci == 0) printn(queue);
}