SE_CodeGolf_42536

int[] A(int n)
{
    int m = n, i, c = 0,l = (int)((n / 2f) * (n + 1));
    var a = new int[l];
    while (m-- > 0)
        for (i = m; i++ < n; )
            a[c++] = i;
    return a;
}