51366domain: NAppears in sequencesNumber of ways to place 2 nonattacking zebras on an n X n board.at n=17A172137Number of -n..n arrays x(0..3) of 4 elements with zero sum and nonzero second and third differences.at n=20A200205Numbers k such that (25*10^k - 73) / 3 is prime.at n=25A276845