# A052577 (b-file synthesized from sequence entry) 0 1 1 4 2 26 3 240 4 2904 5 43680 6 786960 7 16531200 8 396789120 9 10713669120 10 321413702400 11 10606692096000 12 381841394457600 13 14891820610867200 14 625456552834713600 15 28145546185236480000 16 1350986237814140928000 17 68900298484208615424000 18 3720616124549638938624000