Kotlin prime number generation

GeneratePrimes.kt

import kotlin.coroutines.experimental.buildIterator
import kotlin.coroutines.experimental.buildSequence

///not tail recursive!
fun primes(n: Int = 2): Sequence<Int> = buildSequence<Int> {
    yield(n)
    yieldAll(primes(n + 1).filter { x: Int -> x % n != 0 })
}

///tail recursive version
val primesTR = {
    var n = 2
    var acc: MutableList<Int> = mutableListOf()
    generateSequence {
        tailrec fun next(): Int {
            if (acc.none { n % it == 0 }) {
                acc.add(n)
                return n
            }
            else {
                n += 1
                return next()
            }
        }
        next()
    }
}