# A371768 (b-file synthesized from sequence entry) 0 0 1 2 2 6 3 34 4 220 5 1868 6 18648 7 222696 8 3061728 9 48199392 10 852857280 11 16813212480 12 365177928960 13 8671294183680 14 223409173317120 15 6207795845798400 16 185021865565286400 17 5887763630809804800 18 199220359130518118400 19 7141874528908565913600 20 270391380094261923840000