# A068777 (b-file synthesized from sequence entry) 1 0 2 2 3 6 4 24 5 80 6 240 7 896 8 3584 9 15360 10 65792 11 270336 12 1081344 13 4259840 14 16773120 15 66584576 16 266338304 17 1069547520 18 4295032832 19 17213423616 20 68853694464 21 275146342400 22 1099510579200 23 4395899027456 24 17583596109824 25 70351564308480 26 281474993487872