38813domain: NAppears in sequencesRelative of Hofstadter Q-sequence: a(n) = max(0, n+19395) for n <= 0; a(n) = a(n-a(n-1)) + a(n-a(n-2)) + a(n-a(n-3)) for n > 0.at n=28A283886Number of subsets of Z_n such that every ordered pair of distinct elements has a different difference.at n=31A382399