https://www.codingame.com/training/medium/conway-sequence

conway.groovy

input = new Scanner(System.in);

r = input.nextInt()
l = input.nextInt()

c = [[r],[1,r]]
(2..l-1).each {
    List list = c[it - 1]
    result = []
    i = 1
    while (i <= list.size()) {
        count = 1
        while (list[i - 1] == list[i]) {
            count++
            i++
        }
        result.add(count)
        result.add(list[i - 1])
        count = 1
        i++
    }
    c.add(result)
}
println(c[l-1].join(" "))