Translation:Seventeen, eighteen, nineteen, twenty
While normally 'ę' only sounds like 'e' at the end of the word, I think it would actually be considered hypercorrectness to make a clear 'ę' in this particular word.
Similarly, Polish almost doesn't have any silent letters, but a few numbers have them, e.g. "pięćdziesiąt", "sześćdziesiąt", "dziewięćdziesiąt" in which you usually omit 'ć'. 'ę' should be pronounced clearly in 50 and 90 though.