# A007181 (b-file synthesized from sequence entry) 1 2 2 2 3 4 4 12 5 30 6 60 7 154 8 404 9 1046 10 2540 11 6720 12 17484 13 46522 14 120300 15 323800 16 856032 17 2315578 18 6151080 19 16745530 20 44921984 21 122790698 22 331148108 23 908909558 24 2465359580 25 6788313198 26 18491757632 27 51067082988