Wilcoxonsig.levels = function (N = 5, n = 3) 
{
    out = combn(1:N, n, FUN = sum)
    Com = choose(N, n)
    out = sort(out)
    c.unique = rev(unique(out))
    cx = c(max(c.unique) + 1, c.unique)
    alpha = NULL
    i = 0
    for (ci in cx) {
        i = i + 1
        alpha[i] = sum(out >= ci)/Com
    }
    cbind(cx, alpha)
}