# A355988 (b-file synthesized from sequence entry) 0 1 1 1 2 2 3 6 4 24 5 120 6 360 7 2520 8 20160 9 60480 10 604800 11 6652800 12 19958400 13 259459200 14 3632428800 15 10897286400 16 174356582400 17 2964061900800 18 8892185702400 19 168951528345600 20 3379030566912000 21 10137091700736000 22 223016017416192000 23 5129368400572416000