# A018115 (b-file synthesized from sequence entry) 0 1 1 2 2 5 3 11 4 24 5 53 6 118 7 260 8 576 9 1275 10 2822 11 6246 12 13824 13 30598 14 67723 15 149897 16 331776 17 734341 18 1625364 19 3597522 20 7962624 21 17624184 22 39008732 23 86340516 24 191102976 25 422980417 26 936209559 27 2072172384