16386304domain: NAppears in sequencesa(n) and floor(a(n)/7) are both squares; i.e., squares which remain squares when written in base 7 and last digit is removed.at n=11A055859a(n) = ((n-1)^2*n^2*(n+1)^2)/6 - 2*Sum_{l=2..n}Sum_{k=2..n}(n-k+1)*(n-l+1)*(k-1)*(l-1).at n=23A169801