6166615domain: NAppears in sequencesSum of squares of numbers that can be written as t*n + u*(n+1) for nonnegative integers t,u in exactly one way.at n=12A07646024*a(n)+1 is the numerator of the squared circumradius of a cyclic quadrilateral with sides n, n+1, n+2, n+3.at n=18A351698