C# - the only problem, calculate min Multiple for 2 numbers

private static int GCD(int a, int b)
{
    return a == 0 ? b : GCD(b % a, a);
}
private static List<int> CalcNext(ref int prev, List<int> lst, int cur)
{
    int gcd = GCD(prev,cur);
    lst.Add((prev/gcd)*(cur/gcd)*gcd);
    prev = cur;
    return lst;
}
public static List<int> solve(List<int> a)
{
    int prev = a.ElementAt(0), prevB = prev;
    List<int> ret = a.Skip(1).Aggregate(new List<int>{prev}, (lst,cur)=>CalcNext(ref prev, lst, cur)).ToList();
    ret.Add(a.Last());
    return ret;
}

...not the shortest code though