function (N = 13) 
{
    if (N == 2) 
        return(c(1, 2))
    if (N == 3) 
        return(c(1, 3, 2))
    if (N == 4) 
        return(c(1, 4, 3, 2))
    if (N == 5) 
        return(c(1, 4, 5, 3, 2))
    FLAG = F
    if (N%%2 == 0) {
        FLAG = T
        N = N + 1
    }
    k = N - 1
    z = rep(c(1, 3, 3, 1), length.out = k)
    z = matrix(z, byrow = T, ncol = 2)
    z = apply(z, 2, cumsum)
    z01 = matrix(rep(c(1, 0), length.out = k), byrow = T, ncol = 2)
    y = z + z01
    y = t(apply(y, 1, rev))
    if (k%%2 == 0) {
        m = k/2
        if (m%%2 == 0) {
            mat = matrix(1:m, ncol = 2)
        }
        else {
            mat = matrix(rep(1:m, length.out = m + 1), ncol = 2)
        }
        mat = mat[, c(2, 1)]
        mx = nrow(mat)
        mat[, 1] = rev(mat[, 1])
        if (m%%2 != 0) {
            mat[1:(mx - 1), 1] = mat[2:mx, 1]
            mat[mx, 1] = NA
        }
        xord = as.vector(t(mat))
        xord = xord[!is.na(xord)]
    }
    else {
        k = k + 1
        m = k/2
        mat = matrix(1:m, ncol = 2)
        mat = mat[, c(2, 1)]
        mat[, 1] = rev(mat[, 1])
        xord = as.vector(t(mat))
        xord = xord[-length(xord)]
    }
    y[xord, ] = y
    y = as.vector(t(y))
    if (N%%2 == 1) 
        y = c(1, y)
    if (FLAG == T) 
        y = y[y < max(y)]
    y
}