# A162937 (b-file synthesized from sequence entry) 0 1 1 6 2 30 3 150 4 735 5 3600 6 17640 7 86400 8 423210 9 2073000 10 10154040 11 49737000 12 243624060 13 1193330400 14 5845225440 15 28631349600 16 140243381160 17 686946520800 18 3364832751840 19 16481777119200 20 80731791755760 21 395444141299200