public string GetSequence()
{
    string sequence = "[ ";
    sequence += this.ListSequence.Aggregate(
        new StringBuilder(),
        (current, next) => current.Append(current.Length == 0 ? "" : " ").Append(next)).ToString();
    sequence += " ]";

    return sequence;
}
// Produces [ 1 1 2 3 5 8 13 ]