# A026650 (b-file synthesized from sequence entry) 1 1 2 6 3 21 4 108 5 370 6 1908 7 6587 8 34248 9 119142 10 623700 11 2182818 12 11487528 13 40391988 14 213451560 15 753295635 16 3993910416 17 14136717574 18 75152083716 19 266650874678 20 1420670333640 21 5050926317724 22 26960309526744 23 96015725922014