# A006657 (b-file synthesized from sequence entry) 2 2 3 12 4 84 5 640 6 5236 7 45164 8 406012 9 3772008 10 35994184 11 351173328 12 3490681428 13 35253449296 14 360946635312 15 3739935635756 16 39159200588780 17 413836299216608 18 4409705753032648 19 47337525317450816 20 511563350415103008