# A012584 (b-file synthesized from sequence entry) 0 1 1 1 2 3 3 9 4 33 5 145 6 715 7 3801 8 21889 9 140001 10 974803 11 6947017 12 50720417 13 421135793 14 3950147227 15 33562929817 16 240061039105 17 2672302901185 18 45695167547043 19 388308372326665 20 -1858226878271967 21 9709607588675537