# A006660 (b-file synthesized from sequence entry) 3 1 4 1 5 2 6 3 7 7 8 14 9 36 10 81 11 221 12 538 13 1530 14 3926 15 11510 16 30694 17 92114 18 252939 19 773259 20 2172830 21 6743122 22 19304190 23 60658606 24 176343390 25 559952824 26 1649008456 27 5283239596 28 15730575554 29 50789908772 30 152663683494