# A002220 (b-file synthesized from sequence entry) 1 1 2 4 3 10 4 30 5 65 6 173 7 343 8 778 9 1518 10 3088 11 5609 12 10959 13 18990 14 34441 15 58903 16 102044 17 167499 18 282519 19 451529 20 737208 21 1160102 22 1836910 23 2828466 24 4410990 25 6670202 26 10161240 27 15186315 28 22758131 29 33480869