# A009346 (b-file synthesized from sequence entry) 0 0 1 1 2 -1 3 2 4 -6 5 16 6 -72 7 440 8 -2800 9 20224 10 -169984 11 1582976 12 -16076544 13 178612864 14 -2155087872 15 27969867008 16 -388732745728 17 5765737517056 18 -90872771018752 19 1516228355846144 20 -26703924688453632 21 495092243779256320