# A095823 (b-file synthesized from sequence entry) 1 1 2 4 3 18 4 32 5 600 6 4320 7 11760 8 322560 9 3265920 10 1728000 11 439084800 12 821145600 13 817689600 14 1220496076800 15 19615115520000 16 111588212736000 17 863812325376000 18 115242726703104000 19 15722836107264000 20 3742926166425600000