# A005980 (b-file synthesized from sequence entry) 0 1 1 0 2 2 3 4 4 9 5 16 6 35 7 63 8 129 9 234 10 445 11 798 12 1458 13 2568 14 4561 15 7924 16 13770 17 23584 18 40301 19 68097 20 114646 21 191336 22 317893 23 524396 24 861054 25 1405130 26 2282651 27 3688254 28 5933463