This paper gives results on four diverse topics. The first result is that the error term for the number of integers 2u3v≤n is O((logn)1−δ) with δ=(240(log3))−1, using a theorem of A. Baker and G. Wüstholz. The second result is an averaged explicit formulaψ(x)=x−1T∫2TT(∑|γ|≤τxρρ)dτ+O(logxlogxT⋅xT)
for x≫T≫1. It then follows, by the Riemann hypothesis, that ψ(x+h)−ψ(x)=h+O(hλ1/2) if h=λx1/2logx. The third theme tightens the log powers in the zero density bounds of Ingham and Huxley, and gives corollaries for the mean-value of ψ(x+h)−ψ(x)−h. The fourth remark concerns a hypothetical improvement in the constant 2 in the Brun-Titchmarsh theorem, averaged over congruence classes, and its consequence for L(1,χ).