# A007201 (b-file synthesized from sequence entry) 3 24 4 84 5 264 6 1128 7 4728 8 20304 9 86496 10 369732 11 1573608 12 6703068 13 28474704 14 120922272 15 512524704 16 2171836752 17 9190071984 18 38866395264 19 164191075824 20 693230730864