# A153296 (b-file synthesized from sequence entry) 0 1 1 1 2 5 3 29 4 180 5 1162 6 7698 7 51950 8 355531 9 2460224 10 17178755 11 120861710 12 855828960 13 6094211829 14 43610311298 15 313449094851 16 2261820356684 17 16379528485200 18 119003715014955 19 867198605427231 20 6336861345197670