# A215587 (b-file synthesized from sequence entry) 0 1 1 0 2 0 3 3 4 0 5 10 6 90 7 308 8 1680 9 13560 10 123480 11 788568 12 7646760 13 76432720 14 841320480 15 8436217208 16 103473901440 17 1320024546240 18 17546621595840 19 235942960528128 20 3481689023521920 21 54132188358133120 22 858287202343992960 23 14187715233218409728 24 246498724782915369600