iwu2.js

function sequences(n) {
    let result = [];
    if (n < 1) {
      return result
    }
    result.push('1')
    for (let i = 1; i<n; i++) {
      prev = result[i-1].split('-').reverse().join('-')
      result.push(i%2 ? `${i+1}-${prev}` : `${prev}-${i+1}`)
    }

    result.forEach((r) => console.log(r));
    return result;
}

sequences(7)