# A051042 (b-file synthesized from sequence entry) 0 1 1 3 2 9 3 24 4 66 5 180 6 486 7 1314 8 3558 9 9606 10 25956 11 70134 12 189462 13 511866 14 1382880 15 3735888 16 10092762 17 27266340 18 73661610 19 199001490 20 537615066 21 1452399978 22 3923748270