# A048119 (b-file synthesized from sequence entry) 2 1 3 3 4 9 5 30 6 102 7 360 8 1290 9 4704 10 17334 11 64512 12 241836 13 912384 14 3459876 15 13178988 16 50389236 17 193295652 18 743610528 19 2867892588 20 11085281328 21 42933166380 22 166575534264 23 647329281456 24 2519234973996 25 9817121868084