# A201720 (b-file synthesized from sequence entry) 0 0 1 1 2 3 3 12 4 64 5 420 6 3246 7 28798 8 288072 9 3205044 10 39234340 11 523821936 12 7572221328 13 117792884872 14 1961516974704 15 34807390821960 16 655594811020096 17 13060711726818768 18 274358217793164912 19 6060159633360214144 20 140404595387426964480