# A153757 (b-file synthesized from sequence entry) 1 1 2 2 3 4 4 10 5 40 6 280 7 3400 8 68920 9 2296600 10 124819000 11 11029312600 12 1581276391000 13 367448845658200 14 138299522459392600 15 84276864426837376600 16 83129040425047907584600 17 132705616446736897029760600 18 342829213074356555028732544600