52786domain: NAppears in sequencesSemiprimes in A054556.at n=30A113693Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, 0, 1), (0, 1, -1), (0, 1, 1), (1, -1, 1)}.at n=10A148831a(n) = Sum_{1 <= i <= j <= k <= m <= n} gcd(i,j,k,m).at n=30A344992