# A034750 (b-file synthesized from sequence entry) 1 1 2 2 3 4 4 9 5 20 6 64 7 216 8 906 9 4178 10 21222 11 116064 12 678790 13 4213830 14 27645030 15 190899972 16 1382960445 17 10480143744 18 82864876682 19 682076810340 20 5832742233094 21 51724158246750 22 474869816290526 23 4506715738475980