# A018509 (b-file synthesized from sequence entry) 1 1 2 2 3 3 4 4 5 5 6 6 7 9 8 10 9 12 10 15 11 18 12 20 13 27 14 30 15 36 16 45 17 54 18 60 19 90 20 108 21 135 22 180 23 270 24 540