# Josua Kugler, Christian Merten

rec_series <- function(start, f, n, m = length(start)) {
    if (length(start) >= n) return(start)
    rec_series(c(start, f(tail(start, m))), f, n, m)
}

rec_series(rep(1, 2), sum, 16)
rec_series(rep(1, 3), sum, 16)
rec_series(rep(1, 4), sum, 16)
rec_series(c(1,1), function(x) 2*x[1]+x[2], 16)
rec_series(c(1,1), function(x) x[2]-x[1], 16)
rec_series(1:5, mean, 16)
rec_series(1:5, median, 16)