179608domain: NAppears in sequencesa(n) = Sum_{i=1..n, j=1..n, gcd(i,j)=1} (n+1-i)*(n+1-j).at n=31A115004Expansion of Product_{k>=1} (1 + x^k)^(d(k)-1), where d(k) = number of divisors of k (A000005).at n=52A318844Number of mutual-visibility sets in the n-Moebius ladder.at n=16A389185