33746domain: NAppears in sequencesa(n) is the total number of elements in all sum-free subsets of {1,...,n}.at n=18A288888a(n) is the number of distinct solution sets to the quadratic equations u*x^2 + v*x + w = 0 with integer coefficients u, v, w, abs(u) + abs(v) + abs(w) <= n having a nonnegative discriminant.at n=44A379597