# A245373 (b-file synthesized from sequence entry) 0 1 1 2 2 6 3 20 4 80 5 368 6 1904 7 10880 8 67904 9 459008 10 3336704 11 25925120 12 214175744 13 1873092608 14 17276401664 15 167504076800 16 1702214549504 17 18084149854208 18 200388963958784 19 2311212530401280 20 27693720143396864 21 344157474490155008 22 4428851361694613504 23 58933575269230837760