195170domain: NAppears in sequencesT(n,n-1), array T as in A054090.at n=9A054093Number of quadruples [i,j,k,l] with all entries between 1 and n such that gcd(i,j) = gcd(k,l).at n=25A124162a(n) = 1681*n^2 - 756*n + 85.at n=10A157010Coefficient of x^n in the expansion of 1 / ( (1-x) * (1-x+x^2)^2 )^n.at n=7A372462