# A005397 (b-file synthesized from sequence entry) 3 4 4 0 5 0 6 4 7 28 8 80 9 120 10 120 11 264 12 1080 13 3120 14 6440 15 11960 16 26688 17 70448 18 179340 19 415796 20 935560 21 2195536 22 5374468 23 13145420 24 31504224 25 74955600 26 180228984 27 438624648 28 1069909344 29 2600077824 30 6310088640 31 15363918432