# A052573 (b-file synthesized from sequence entry) 0 2 1 4 2 20 3 168 4 1968 5 29280 6 525600 7 11027520 8 264579840 9 7142929920 10 214280640000 11 7071181286400 12 254561568307200 13 9927888709939200 14 416971151460864000 15 18763699200390144000 16 900657519773147136000