# A082526 (b-file synthesized from sequence entry) 0 1 1 1 2 1 3 2 4 3 5 12 6 40 7 120 8 2520 9 5040 10 10080 11 5040 12 19958400 13 19958400 14 259459200 15 518918400 16 2179457280 17 4358914560 18 1235025792000 19 3705077376000 20 422378820864000 21 52797352608000 22 120679663104000 23 844757641728000