Looped list implementation without using loop to get a value with a negative index.

LoopList.cs

using System.Collections.Generic;

public class LoopList<T> : List<T> {

    public new T this[int index] {
        get {
            index = CalculateIndex(index);
            return base[index];
        }

        set {
            index = CalculateIndex(index);
            base[index] = value;
        }
    }

    public LoopList() { }
    public LoopList(IEnumerable<T> collection) : base(collection) { }

    public new void RemoveAt(int index) {
        Remove(this[index]);
    }

    private int CalculateIndex(int index) {
        if (index < 0) {
            int reversedIndex = (index + 1) * -1;

            if (reversedIndex >= Count) {
                index = Count - 1 - (index % Count);
            } else {
                index = reversedIndex;
            }
        } else if (index >= Count) {
            index %= Count;
        }

        return index;
    }
}