# A052628 (b-file synthesized from sequence entry) 0 2 1 2 2 4 3 18 4 48 5 240 6 1440 7 10080 8 80640 9 725760 10 7257600 11 79833600 12 958003200 13 12454041600 14 174356582400 15 2615348736000 16 41845579776000 17 711374856192000 18 12804747411456000 19 243290200817664000