365408domain: NAppears in sequencesNumbers k such that phi(k)*sigma(k) is a triangular number.at n=19A115911Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 1), (-1, 0, 1), (0, 0, 1), (0, 1, 1), (1, 1, -1)}.at n=10A150169