# A001180 (b-file synthesized from sequence entry) 1 1 2 1 3 2 4 3 5 3 6 5 7 9 8 16 9 28 10 50 11 89 12 159 13 285 14 510 15 914 16 1639 17 2938 18 5269 19 9451 20 16952