# A069143 (b-file synthesized from sequence entry) 1 1 2 1 3 3 4 7 5 18 6 31 7 57 8 180 9 320 10 1092 11 2478 12 10368 13 25704 14 100800 15 393120 16 1965600 17 10326624 18 39657600 19 131580288 20 511223790 21 1469266560 22 4911616440 23 22120488000 24 95841111600 25 460020244320 26 2163425531904 27 9805180170240