How to do it...

1. Declare a function called fibonacci() and use the generateSequence() function to define a formula for the next elements of the sequence:

fun fibonacci(): Sequence<Int> {
    return generateSequence(Pair(0, 1)) { Pair(it.second, it.first + it.second) }
            .map { it.first }
}

2. Use the fibonacci() function to print the next Fibonacci numbers to the console:

println(fibonacci().take(20).toList())