# A068200 (b-file synthesized from sequence entry) 0 1 1 2 2 6 3 24 4 120 5 696 6 4536 7 32568 8 254136 9 2133816 10 19130040 11 182000952 12 1828296888 13 19311334200 14 213709376184 15 2470302259512 16 29746381049016 17 372270346391352 18 4831940144914104 19 64925998174811448 20 901626111996723384 21 12920858504042924856