I found this puzzle today. I have not tried it myself. But I think you will know when you get the right answer. Further, unlike other times, I am writing this to you on my way out of Atlanta as I commence my business trip, not on my return trip. Which means, I may not be able to check answers till the end of day or in flights…
Do send personal messages only and not comments.

Arrange 16 coins in a simple square of 4 coins by 4 coins. Now, remove 6 coins in a way that every row and every column still has even number of coins left.