# A027991 (b-file synthesized from sequence entry) 1 1 2 3 3 12 4 40 5 130 6 404 7 1227 8 3653 9 10720 10 31090 11 89316 12 254568 13 720757 14 2029095 15 5684340 16 15855964 17 44061862 18 122032508 19 336966015 20 927953705 21 2549229256 22 6987648358 23 19115124552 24 52194037200 25 142274514025 26 387215773899