I suspect it was this one? https://terrytao.wordpress.com/2011/08/25/the-collatz-conjecture-littlewood-offord-theory-and-powers-of-2-and-3/#comment-84973 https:

I suspect it was this one? https://terrytao.wordpress.com/2011/08/25/the-collatz-conjecture-littlewood-offord-theory-and-powers-of-2-and-3/#comment-84973 https://terrytao.wordpress.com/2011/08/25/the-collatz-conjec...