336895domain: NAppears in sequencesNumber of n X n binary arrays symmetric under 90-degree rotation with all ones connected only in a zee 1,1 1,2 2,2 2,3 in any orientation.at n=13A145958a(n) = Sum_{j=1..n*(n-1)} (n*j mod (n+j)).at n=31A309341a(n) = Sum_{k=1..n} k * sigma_2(k).at n=31A356125