# A002919 (b-file synthesized from sequence entry) 0 1 1 6 2 24 3 90 4 318 5 1098 6 3696 7 12270 8 40224 9 130650 10 421176 11 1348998 12 4299018 13 13635630 14 43092888 15 135698970 16 426144654 17 1334488074 18 4170038328 19 13001153910 20 40464412482 21 125706293478 22 389962873920 23 1207855307874 24 3736709089176 25 11544946664622 26 35633199126576