# A375634 (b-file synthesized from sequence entry) 0 1 1 1 2 2 3 12 4 52 5 280 6 2160 7 16870 8 150080 9 1557360 10 17491600 11 215908000 12 2923905600 13 42734091400 14 672515043200 15 11347480544400 16 204142655516800 17 3902009862150400 18 78976503077472000 19 1687212801048174400 20 37941749192547200000