# A056270 (b-file synthesized from sequence entry) 1 0 2 0 3 0 4 0 5 120 6 1800 7 16800 8 126000 9 834120 10 5102880 11 29607600 12 165526200 13 901020120 14 4808987400 15 25292030280 16 131542740000 17 678330198120 18 3474970629480 19 17710714165200 20 89904725757000