# A007172 (b-file synthesized from sequence entry) 1 1 2 1 3 1 4 3 5 7 6 24 7 93 8 434 9 2110 10 10957 11 58713 12 321576 13 1792133 14 10131027 15 57949430 16 334970205 17 1953890318 18 11489753730 19 68054102361 20 405715557048