# A018116 (b-file synthesized from sequence entry) 0 1 1 3 2 5 3 11 4 24 5 54 6 118 7 261 8 576 9 1275 10 2822 11 6246 12 13824 13 30598 14 67724 15 149897 16 331776 17 734342 18 1625364 19 3597522 20 7962624 21 17624185 22 39008732 23 86340517 24 191102976 25 422980417 26 936209560 27 2072172385