# A148980 (b-file synthesized from sequence entry) 0 1 1 1 2 3 3 9 4 32 5 112 6 416 7 1600 8 6303 9 25287 10 103015 11 425429 12 1777767 13 7500273 14 31915140 15 136814101 16 590457109 17 2563483906 18 11188928245 19 49072703877 20 216169809953 21 956076808622 22 4244091355887 23 18903499430285 24 84460316766813 25 378457183512630 26 1700378927500223 27 7658769324015511 28 34576775876824113