110823domain: NAppears in sequencesNumber of (n+1) X 2 0..3 arrays with every 2 X 2 subblock having nonzero determinant and commuting with every horizontal or vertical neighbor.at n=12A206336Least k such that the sum of the semiprime divisors equals n times the sum of the prime divisors, or 0 if no such k exists.at n=34A227419