# A335287 (b-file synthesized from sequence entry) 1 1 2 2 3 6 4 12 5 30 6 168 7 210 8 420 9 840 10 9240 11 83160 12 120120 13 5165160 14 26860680 15 277560360 16 569729160 17 16522145640 18 33044291280 19 563462139240 20 1140028049160 21 1255683068640 22 65361608151840 23 299761858075680 24 413956851628320